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bbe5fb7821
The chromatic dispersion and dispersion slope can be provided as a single values evaluated at the fiber reference frequency or in a dictionary containing the dispersion values evaluated at multiple frequencies:
"dispersion": {"value": [], "frequency": []}
Change-Id: I81429484dd373cc49bd9baf013247782ba1912fd
650 lines
47 KiB
ReStructuredText
650 lines
47 KiB
ReStructuredText
.. _legacy-json:
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JSON Input Files
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================
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GNPy uses a set of JSON files for modeling the network.
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Some data (such as network topology or the service requests) can be also passed via :ref:`XLS files<excel-service-sheet>`.
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Equipment Library
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-----------------
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Design and transmission parameters are defined in a dedicated json file.
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By default, this information is read from `gnpy/example-data/eqpt_config.json <https://github.com/Telecominfraproject/oopt-gnpy/blob/master/gnpy/example-data/eqpt_config.json>`_.
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This file defines the equipment libraries that can be customized (EDFAs, fibers, and transceivers).
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It also defines the simulation parameters (spans, ROADMs, and the spectral information to transmit.)
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EDFA
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~~~~
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The EDFA equipment library is a list of supported amplifiers. New amplifiers
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can be added and existing ones removed. Three different noise models are available:
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1. ``'type_def': 'variable_gain'`` is a simplified model simulating a 2-coil EDFA with internal, input and output VOAs.
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The NF vs gain response is calculated accordingly based on the input parameters: ``nf_min``, ``nf_max``, and ``gain_flatmax``.
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It is not a simple interpolation but a 2-stage NF calculation.
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2. ``'type_def': 'fixed_gain'`` is a fixed gain model.
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`NF == Cte == nf0` if `gain_min < gain < gain_flatmax`
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3. ``'type_def': 'openroadm'`` models the incremental OSNR contribution as a function of input power.
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It is suitable for inline amplifiers that conform to the OpenROADM specification.
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The input parameters are coefficients of the :ref:`third-degree polynomial<ext-nf-model-polynomial-OSNR-OpenROADM>`.
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4. ``'type_def': 'openroadm_preamp'`` and ``openroadm_booster`` approximate the :ref:`preamp and booster within an OpenROADM network<ext-nf-model-noise-mask-OpenROADM>`.
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No extra parameters specific to the NF model are accepted.
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5. ``'type_def': 'advanced_model'`` is an advanced model.
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A detailed JSON configuration file is required (by default `gnpy/example-data/std_medium_gain_advanced_config.json <https://github.com/Telecominfraproject/oopt-gnpy/blob/master/gnpy/example-data/std_medium_gain_advanced_config.json>`_).
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It uses a 3rd order polynomial where NF = f(gain), NF_ripple = f(frequency), gain_ripple = f(frequency), N-array dgt = f(frequency).
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Compared to the previous models, NF ripple and gain ripple are modelled.
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For all amplifier models:
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+------------------------+-----------+-----------------------------------------+
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| field | type | description |
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+========================+===========+=========================================+
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| ``type_variety`` | (string) | a unique name to ID the amplifier in the|
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| | | JSON/Excel template topology input file |
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+------------------------+-----------+-----------------------------------------+
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| ``out_voa_auto`` | (boolean) | auto-design feature to optimize the |
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| | | amplifier output VOA. If true, output |
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| | | VOA is present and will be used to push |
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| | | amplifier gain to its maximum, within |
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| | | EOL power margins. |
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+------------------------+-----------+-----------------------------------------+
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| ``allowed_for_design`` | (boolean) | If false, the amplifier will not be |
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| | | picked by auto-design but it can still |
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| | | be used as a manual input (from JSON or |
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| | | Excel template topology files.) |
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+------------------------+-----------+-----------------------------------------+
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Fiber
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~~~~~
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The fiber library currently describes SSMF and NZDF but additional fiber types can be entered by the user following the same model:
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+------------------------------+-----------------+------------------------------------------------+
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| field | type | description |
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+==============================+=================+================================================+
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| ``type_variety`` | (string) | a unique name to ID the fiber in the |
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| | | JSON or Excel template topology input |
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| | | file |
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+------------------------------+-----------------+------------------------------------------------+
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| ``dispersion`` | (number) | In :math:`s \times m^{-1} \times m^{-1}`. |
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+------------------------------+-----------------+------------------------------------------------+
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| ``dispersion_slope`` | (number) | In :math:`s \times m^{-1} \times m^{-1} |
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| | | \times m^{-1}` |
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+------------------------------+-----------------+------------------------------------------------+
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| ``dispersion_per_frequency`` | (dict) | Dictionary of dispersion values evaluated at |
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| | | various frequencies, as follows: |
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| | | ``{"value": [], "frequency": []}``. |
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| | | ``value`` in |
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| | | :math:`s \times m^{-1} \times m^{-1}` and |
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| | | ``frequency`` in Hz. |
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+------------------------------+-----------------+------------------------------------------------+
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| ``effective_area`` | (number) | Effective area of the fiber (not just |
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| | | the MFD circle). This is the |
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| | | :math:`A_{eff}`, see e.g., the |
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| | | `Corning whitepaper on MFD/EA`_. |
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| | | Specified in :math:`m^{2}`. |
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+------------------------------+-----------------+------------------------------------------------+
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| ``gamma`` | (number) | Coefficient :math:`\gamma = 2\pi\times |
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| | | n^2/(\lambda*A_{eff})`. |
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| | | If not provided, this will be derived |
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| | | from the ``effective_area`` |
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| | | :math:`A_{eff}`. |
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| | | In :math:`w^{-1} \times m^{-1}`. |
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| | | This quantity is evaluated at the |
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| | | reference frequency and it is scaled |
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| | | along frequency accordingly to the |
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| | | effective area scaling. |
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+------------------------------+-----------------+------------------------------------------------+
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| ``pmd_coef`` | (number) | Polarization mode dispersion (PMD) |
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| | | coefficient. In |
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| | | :math:`s\times\sqrt{m}^{-1}`. |
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+------------------------------+-----------------+------------------------------------------------+
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| ``lumped_losses`` | (array) | Places along the fiber length with extra |
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| | | losses. Specified as a loss in dB at |
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| | | each relevant position (in km): |
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| | | ``{"position": 10, "loss": 1.5}``) |
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+------------------------------+-----------------+------------------------------------------------+
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| ``raman_coefficient`` | (dict) | The fundamental parameter that describes |
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| | | the regulation of the power transfer |
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| | | between channels during fiber propagation |
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| | | is the Raman gain coefficient (see |
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| | | :cite:`DAmicoJLT2022` for further |
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| | | details); :math:`f_{ref}` represents the |
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| | | pump reference frequency used for the |
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| | | Raman gain coefficient profile |
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| | | measurement ("reference_frequency"), |
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| | | :math:`\Delta f` is the frequency shift |
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| | | between the pump and the specific Stokes |
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| | | wave, the Raman gain coefficient |
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| | | in terms of optical power |
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| | | :math:`g_0`, expressed in |
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| | | :math:`1/(m\;W)`. |
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| | | Default values measured for a SSMF are |
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| | | considered when not specified. |
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+------------------------------+-----------------+------------------------------------------------+
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.. _Corning whitepaper on MFD/EA: https://www.corning.com/microsites/coc/oem/documents/specialty-fiber/WP7071-Mode-Field-Diam-and-Eff-Area.pdf
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RamanFiber
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~~~~~~~~~~
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The RamanFiber can be used to simulate Raman amplification through dedicated Raman pumps. The Raman pumps must be listed
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in the key ``raman_pumps`` within the RamanFiber ``operational`` dictionary. The description of each Raman pump must
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contain the following:
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+---------------------------+-----------+------------------------------------------------------------+
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| field | type | description |
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+===========================+===========+============================================================+
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| ``power`` | (number) | Total pump power in :math:`W` |
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| | | considering a depolarized pump |
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+---------------------------+-----------+------------------------------------------------------------+
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| ``frequency`` | (number) | Pump central frequency in :math:`Hz` |
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+---------------------------+-----------+------------------------------------------------------------+
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| ``propagation_direction`` | (number) | The pumps can propagate in the same or opposite direction |
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| | | with respect the signal. Valid choices are ``coprop`` and |
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| | | ``counterprop``, respectively |
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+---------------------------+-----------+------------------------------------------------------------+
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Beside the list of Raman pumps, the RamanFiber ``operational`` dictionary must include the ``temperature`` that affects
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the amplified spontaneous emission noise generated by the Raman amplification.
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As the loss coefficient significantly varies outside the C-band, where the Raman pumps are usually placed,
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it is suggested to include an estimation of the loss coefficient for the Raman pump central frequencies within
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a dictionary-like definition of the ``RamanFiber.params.loss_coef``
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(e.g. ``loss_coef = {"value": [0.18, 0.18, 0.20, 0.20], "frequency": [191e12, 196e12, 200e12, 210e12]}``).
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Transceiver
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~~~~~~~~~~~
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The transceiver equipment library is a list of supported transceivers. New
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transceivers can be added and existing ones removed at will by the user. It is
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used to determine the service list path feasibility when running the
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``gnpy-path-request`` script.
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+----------------------+-----------+-----------------------------------------+
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| field | type | description |
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+======================+===========+=========================================+
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| ``type_variety`` | (string) | A unique name to ID the transceiver in |
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| | | the JSON or Excel template topology |
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| | | input file |
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+----------------------+-----------+-----------------------------------------+
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| ``frequency`` | (number) | Min/max central channel frequency. |
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+----------------------+-----------+-----------------------------------------+
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| ``mode`` | (number) | A list of modes supported by the |
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| | | transponder. New modes can be added at |
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| | | will by the user. The modes are specific|
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| | | to each transponder type_variety. |
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| | | Each mode is described as below. |
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+----------------------+-----------+-----------------------------------------+
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The modes are defined as follows:
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+----------------------+-----------+-----------------------------------------+
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| field | type | description |
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+======================+===========+=========================================+
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| ``format`` | (string) | a unique name to ID the mode |
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+----------------------+-----------+-----------------------------------------+
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| ``baud_rate`` | (number) | in Hz |
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+----------------------+-----------+-----------------------------------------+
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| ``OSNR`` | (number) | min required OSNR in 0.1nm (dB) |
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+----------------------+-----------+-----------------------------------------+
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| ``bit_rate`` | (number) | in bit/s |
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+----------------------+-----------+-----------------------------------------+
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| ``roll_off`` | (number) | Pure number between 0 and 1. TX signal |
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| | | roll-off shape. Used by Raman-aware |
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| | | simulation code. |
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+----------------------+-----------+-----------------------------------------+
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| ``tx_osnr`` | (number) | In dB. OSNR out from transponder. |
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+----------------------+-----------+-----------------------------------------+
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| ``cost`` | (number) | Arbitrary unit |
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+----------------------+-----------+-----------------------------------------+
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ROADM
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~~~~~
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The user can only modify the value of existing parameters:
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+-------------------------------+-----------+----------------------------------------------------+
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| field | type | description |
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+===============================+===========+====================================================+
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| ``target_pch_out_db`` | (number) | Default :ref:`equalization strategy<equalization>` |
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| or | | for this ROADM type. |
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| ``target_psd_out_mWperGHz`` | | |
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| or | | Auto-design sets the ROADM egress channel |
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| ``target_out_mWperSlotWidth`` | | power. This reflects typical control loop |
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| (mutually exclusive) | | algorithms that adjust ROADM losses to |
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| | | equalize channels (e.g., coming from |
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| | | different ingress direction or add ports). |
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| | | These values are used as defaults when no |
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| | | overrides are set per each ``Roadm`` |
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| | | element in the network topology. |
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+-------------------------------+-----------+----------------------------------------------------+
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| ``add_drop_osnr`` | (number) | OSNR contribution from the add/drop ports |
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+-------------------------------+-----------+----------------------------------------------------+
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| ``pmd`` | (number) | Polarization mode dispersion (PMD). (s) |
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+-------------------------------+-----------+----------------------------------------------------+
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| ``restrictions`` | (dict of | If non-empty, keys ``preamp_variety_list`` |
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| | strings) | and ``booster_variety_list`` represent |
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| | | list of ``type_variety`` amplifiers which |
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| | | are allowed for auto-design within ROADM's |
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| | | line degrees. |
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| | | |
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| | | If no booster should be placed on a degree, |
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| | | insert a ``Fused`` node on the degree |
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| | | output. |
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+-------------------------------+-----------+----------------------------------------------------+
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Global parameters
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-----------------
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The following options are still defined in ``eqpt_config.json`` for legacy reasons, but
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they do not correspond to tangible network devices.
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Auto-design automatically creates EDFA amplifier network elements when they are missing, after a fiber, or between a ROADM and a fiber.
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This auto-design functionality can be manually and locally deactivated by introducing a ``Fused`` network element after a ``Fiber`` or a ``Roadm`` that doesn't need amplification.
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The amplifier is chosen in the EDFA list of the equipment library based on gain, power, and NF criteria.
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Only the EDFA that are marked ``'allowed_for_design': true`` are considered.
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For amplifiers defined in the topology JSON input but whose ``gain = 0`` (placeholder), auto-design will set its gain automatically: see ``power_mode`` in the ``Spans`` library to find out how the gain is calculated.
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The file ``sim_params.json`` contains the tuning parameters used within both the ``gnpy.science_utils.RamanSolver`` and
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the ``gnpy.science_utils.NliSolver`` for the evaluation of the Raman profile and the NLI generation, respectively.
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If amplifiers don't have settings, auto-design also sets amplifiers gain, output VOA and target powers according to [J. -L. Auge, V. Curri and E. Le Rouzic, Open Design for Multi-Vendor Optical Networks, OFC 2019](https://ieeexplore.ieee.org/document/8696699), equation 4.
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See ``delta_power_range_db`` for more explaination.
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+---------------------------------------------+-----------+---------------------------------------------+
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| field | type | description |
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+=============================================+===========+=============================================+
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| ``raman_params.flag`` | (boolean) | Enable/Disable the Raman effect that |
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| | | produces a power transfer from higher to |
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| | | lower frequencies. |
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| | | In general, considering the Raman effect |
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| | | provides more accurate results. It is |
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| | | mandatory when Raman amplification is |
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| | | included in the simulation |
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+---------------------------------------------+-----------+---------------------------------------------+
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| ``raman_params.result_spatial_resolution`` | (number) | Spatial resolution of the output |
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| | | Raman profile along the entire fiber span. |
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| | | This affects the accuracy and the |
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| | | computational time of the NLI |
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| | | calculation when the GGN method is used: |
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| | | smaller the spatial resolution higher both |
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| | | the accuracy and the computational time. |
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| | | In C-band simulations, with input power per |
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| | | channel around 0 dBm, a suggested value of |
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| | | spatial resolution is 10e3 m |
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+---------------------------------------------+-----------+---------------------------------------------+
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| ``raman_params.solver_spatial_resolution`` | (number) | Spatial step for the iterative solution |
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| | | of the first order differential equation |
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| | | used to calculate the Raman profile |
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| | | along the entire fiber span. |
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| | | This affects the accuracy and the |
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| | | computational time of the evaluated |
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| | | Raman profile: |
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| | | smaller the spatial resolution higher both |
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| | | the accuracy and the computational time. |
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| | | In C-band simulations, with input power per |
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| | | channel around 0 dBm, a suggested value of |
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| | | spatial resolution is 100 m |
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+---------------------------------------------+-----------+---------------------------------------------+
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| ``nli_params.method`` | (string) | Model used for the NLI evaluation. Valid |
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| | | choices are ``gn_model_analytic`` (see |
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| | | eq. 120 from `arXiv:1209.0394 |
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| | | <https://arxiv.org/abs/1209.0394>`_) and |
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| | | ``ggn_spectrally_separated`` (see eq. 21 |
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| | | from `arXiv:1710.02225 |
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| | | <https://arxiv.org/abs/1710.02225>`_). |
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+---------------------------------------------+-----------+---------------------------------------------+
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| ``nli_params.computed_channels`` | (number) | The channels on which the NLI is |
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| | | explicitly evaluated. |
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| | | The NLI of the other channels is |
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| | | interpolated using ``numpy.interp``. |
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| | | In a C-band simulation with 96 channels in |
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| | | a 50 GHz spacing fix-grid we recommend at |
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| | | one computed channel every 20 channels. |
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+---------------------------------------------+-----------+---------------------------------------------+
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Span
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~~~~
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Span configuration is not a list (which may change in later releases) and the user can only modify the value of existing parameters:
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+-------------------------------------+-----------+---------------------------------------------+
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| field | type | description |
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+=====================================+===========+=============================================+
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| ``power_mode`` | (boolean) | If false, **gain mode**. In the gain mode, |
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| | | only gain settings are used for |
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| | | propagation, and ``delta_p`` is ignored. |
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| | | If no ``gain_target`` is set in an |
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| | | amplifier, auto-design computes one |
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| | | according to the ``delta_power_range`` |
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| | | optimisation range. |
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| | | The gain mode |
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| | | is recommended if all the amplifiers |
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| | | have already consistent gain settings in |
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| | | the topology input file. |
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| | | |
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| | | If true, **power mode**. In the power mode, |
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| | | only the ``delta_p`` is used for |
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| | | propagation, and ``gain_target`` is |
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| | | ignored. |
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| | | The power mode is recommended for |
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| | | auto-design and power sweep. |
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| | | If no ``delta_p`` is set, |
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| | | auto-design sets an amplifier power target |
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| | | according to delta_power_range_db. |
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+-------------------------------------+-----------+---------------------------------------------+
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| ``delta_power_range_db`` | (number) | Auto-design only, power-mode |
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| | | only. Specifies the [min, max, step] |
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| | | power excursion/span. It is a relative |
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| | | power excursion w/r/t the |
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| | | power_dbm + power_range_db |
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| | | (power sweep if applicable) defined in |
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| | | the SI configuration library. This |
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| | | relative power excursion is = 1/3 of |
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| | | the span loss difference with the |
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| | | reference 20 dB span. The 1/3 slope is |
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| | | derived from the GN model equations. |
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| | | For example, a 23 dB span loss will be |
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| | | set to 1 dB more power than a 20 dB |
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| | | span loss. The 20 dB reference spans |
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| | | will *always* be set to |
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| | | power = power_dbm + power_range_db. |
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| | | To configure the same power in all |
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| | | spans, use `[0, 0, 0]`. All spans will |
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| | | be set to |
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| | | power = power_dbm + power_range_db. |
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| | | To configure the same power in all spans |
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| | | and 3 dB more power just for the longest |
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| | | spans: `[0, 3, 3]`. The longest spans are |
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| | | set to |
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| | | power = power_dbm + power_range_db + 3. |
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| | | To configure a 4 dB power range across |
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| | | all spans in 0.5 dB steps: `[-2, 2, 0.5]`. |
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| | | A 17 dB span is set to |
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| | | power = power_dbm + power_range_db - 1, |
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| | | a 20 dB span to |
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| | | power = power_dbm + power_range_db and |
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| | | a 23 dB span to |
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| | | power = power_dbm + power_range_db + 1 |
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+-------------------------------------+-----------+---------------------------------------------+
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| ``max_fiber_lineic_loss_for_raman`` | (number) | Maximum linear fiber loss for Raman |
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| | | amplification use. |
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+-------------------------------------+-----------+---------------------------------------------+
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| ``max_length`` | (number) | Split fiber lengths > max_length. |
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| | | Interest to support high level |
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| | | topologies that do not specify in line |
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| | | amplification sites. For example the |
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| | | CORONET_Global_Topology.xlsx defines |
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| | | links > 1000km between 2 sites: it |
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| | | couldn't be simulated if these links |
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| | | were not split in shorter span lengths. |
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+-------------------------------------+-----------+---------------------------------------------+
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| ``length_unit`` | "m"/"km" | Unit for ``max_length``. |
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+-------------------------------------+-----------+---------------------------------------------+
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| ``max_loss`` | (number) | Not used in the current code |
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| | | implementation. |
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+-------------------------------------+-----------+---------------------------------------------+
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| ``padding`` | (number) | In dB. Min span loss before putting an |
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| | | attenuator before fiber. Attenuator |
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| | | value |
|
|
| | | Fiber.att_in = max(0, padding - span_loss). |
|
|
| | | Padding can be set manually to reach a |
|
|
| | | higher padding value for a given fiber |
|
|
| | | by filling in the Fiber/params/att_in |
|
|
| | | field in the topology json input [1] |
|
|
| | | but if span_loss = length * loss_coef |
|
|
| | | + att_in + con_in + con_out < padding, |
|
|
| | | the specified att_in value will be |
|
|
| | | completed to have span_loss = padding. |
|
|
| | | Therefore it is not possible to set |
|
|
| | | span_loss < padding. |
|
|
+-------------------------------------+-----------+---------------------------------------------+
|
|
| ``EOL`` | (number) | All fiber span loss ageing. The value |
|
|
| | | is added to the con_out (fiber output |
|
|
| | | connector). So the design and the path |
|
|
| | | feasibility are performed with |
|
|
| | | span_loss + EOL. EOL cannot be set |
|
|
| | | manually for a given fiber span |
|
|
| | | (workaround is to specify higher |
|
|
| | | ``con_out`` loss for this fiber). |
|
|
+-------------------------------------+-----------+---------------------------------------------+
|
|
| ``con_in``, | (number) | Default values if Fiber/params/con_in/out |
|
|
| ``con_out`` | | is None in the topology input |
|
|
| | | description. This default value is |
|
|
| | | ignored if a Fiber/params/con_in/out |
|
|
| | | value is input in the topology for a |
|
|
| | | given Fiber. |
|
|
+-------------------------------------+-----------+---------------------------------------------+
|
|
|
|
.. code-block:: json
|
|
|
|
{
|
|
"uid": "fiber (A1->A2)",
|
|
"type": "Fiber",
|
|
"type_variety": "SSMF",
|
|
"params":
|
|
{
|
|
"length": 120.0,
|
|
"loss_coef": 0.2,
|
|
"length_units": "km",
|
|
"att_in": 0,
|
|
"con_in": 0,
|
|
"con_out": 0
|
|
}
|
|
}
|
|
|
|
SpectralInformation
|
|
~~~~~~~~~~~~~~~~~~~
|
|
|
|
GNPy requires a description of all channels that are propagated through the network.
|
|
Flexgrid channel partitioning is available since the 2.7 release via the extra ``--spectrum`` option.
|
|
In the simplest case, homogeneous channel allocation can be defined via the ``SpectralInformation`` construct which defines a spectrum of N identical carriers:
|
|
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| field | type | description |
|
|
+======================+===========+===========================================+
|
|
| ``f_min``, | (number) | In Hz. Define spectrum boundaries. Note |
|
|
| ``f_max`` | | that due to backward compatibility, the |
|
|
| | | first channel central frequency is placed |
|
|
| | | at :math:`f_{min} + spacing` and the last |
|
|
| | | one at :math:`f_{max}`. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``baud_rate`` | (number) | In Hz. Simulated baud rate. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``spacing`` | (number) | In Hz. Carrier spacing. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``roll_off`` | (number) | Pure number between 0 and 1. TX signal |
|
|
| | | roll-off shape. Used by Raman-aware |
|
|
| | | simulation code. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``tx_osnr`` | (number) | In dB. OSNR out from transponder. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``power_dbm`` | (number) | Reference channel power, in dBm. |
|
|
| | | In gain mode |
|
|
| | | (see spans/power_mode = false), if no |
|
|
| | | gain is set in an amplifier, auto-design |
|
|
| | | sets gain to meet this reference |
|
|
| | | power. If amplifiers gain is set, |
|
|
| | | ``power_dbm`` is |
|
|
| | | ignored. |
|
|
| | | |
|
|
| | | In power mode, the ``power_dbm`` |
|
|
| | | is the reference power for |
|
|
| | | the ``delta_p`` settings in amplifiers. |
|
|
| | | It is also the reference power for |
|
|
| | | auto-design power optimisation range |
|
|
| | | Spans/delta_power_range_db. For example, |
|
|
| | | if delta_power_range_db = `[0,0,0]`, the |
|
|
| | | same power=power_dbm is launched in every |
|
|
| | | spans. The network design is performed |
|
|
| | | with the power_dbm value: even if a |
|
|
| | | power sweep is defined (see after) the |
|
|
| | | design is not repeated. |
|
|
| | | |
|
|
| | | If the ``--power`` CLI option is used, |
|
|
| | | its value replaces this parameter. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``power_range_db`` | (number) | Power sweep excursion around |
|
|
| | | ``power_dbm``. |
|
|
| | | This defines a list of reference powers |
|
|
| | | to run the propagation, in the range |
|
|
| | | power_range_db + power_dbm. |
|
|
| | | Power sweep uses the ``delta_p`` targets |
|
|
| | | or, if they have not been set, the ones |
|
|
| | | computed by auto-design, regardless of |
|
|
| | | of preceding amplifiers' power |
|
|
| | | saturation. |
|
|
| | | |
|
|
| | | Power sweep is an easy way to find the |
|
|
| | | optimal reference power. |
|
|
| | | |
|
|
| | | Power sweep excursion is ignored in case |
|
|
| | | of gain mode. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``sys_margins`` | (number) | In dB. Added margin on min required |
|
|
| | | transceiver OSNR. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
|
|
.. _mixed-rate:
|
|
|
|
Arbitrary channel definition
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Non-uniform channels are defined via a list of spectrum "partitions" which are defined in an extra JSON file via the ``--spectrum`` option.
|
|
In this approach, each partition is internally homogeneous, but different partitions might use different channel widths, power targets, modulation rates, etc.
|
|
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| field | type | description |
|
|
+======================+===========+===========================================+
|
|
| ``f_min``, | (number) | In Hz. Mandatory. |
|
|
| ``f_max`` | | Define partition :math:`f_{min}` is |
|
|
| | | the first carrier central frequency |
|
|
| | | :math:`f_{max}` is the last one. |
|
|
| | | :math:`f_{min}` -:math:`f_{max}` |
|
|
| | | partitions must not overlap. |
|
|
| | | |
|
|
| | | Note that the meaning of ``f_min`` and |
|
|
| | | ``f_max`` is different than the one in |
|
|
| | | ``SpectralInformation``. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``baud_rate`` | (number) | In Hz. Mandatory. Simulated baud rate. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``slot_width`` | (number) | In Hz. Carrier spectrum occupation. |
|
|
| | | Carriers of this partition are spaced at |
|
|
| | | ``slot_width`` offsets. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``roll_off`` | (number) | Pure number between 0 and 1. Mandatory |
|
|
| | | TX signal roll-off shape. Used by |
|
|
| | | Raman-aware simulation code. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``tx_osnr`` | (number) | In dB. Optional. OSNR out from |
|
|
| | | transponder. Default value is 40 dB. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
| ``delta_pdb`` | (number) | In dB. Optional. Power offset compared to |
|
|
| | | the reference power used for design |
|
|
| | | (SI block in equipment library) to be |
|
|
| | | applied by ROADM to equalize the carriers |
|
|
| | | in this partition. Default value is 0 dB. |
|
|
+----------------------+-----------+-------------------------------------------+
|
|
|
|
For example this example:
|
|
|
|
.. code-block:: json
|
|
|
|
{
|
|
"SI":[
|
|
{
|
|
"f_min": 191.4e12,
|
|
"f_max":193.1e12,
|
|
"baud_rate": 32e9,
|
|
"slot_width": 50e9,
|
|
"roll_off": 0.15,
|
|
"tx_osnr": 40
|
|
},
|
|
{
|
|
"f_min": 193.1625e12,
|
|
"f_max":195e12,
|
|
"baud_rate": 64e9,
|
|
"delta_pdb": 3,
|
|
"slot_width": 75e9,
|
|
"roll_off": 0.15,
|
|
"tx_osnr": 40
|
|
}
|
|
]
|
|
}
|
|
|
|
...defines a spectrum split into two parts.
|
|
Carriers with central frequencies ranging from 191.4 THz to 193.1 THz will have 32 GBaud rate and will be spaced by 50 Ghz.
|
|
Carriers with central frequencies ranging from 193.1625 THz to 195 THz will have 64 GBaud rate and will be spaced by 75 GHz with 3 dB power offset.
|
|
|
|
If the SI reference carrier is set to ``power_dbm`` = 0dBm, and the ROADM has ``target_pch_out_db`` set to -20 dBm, then all channels ranging from 191.4 THz to 193.1 THz will have their power equalized to -20 + 0 dBm (due to the 0 dB power offset).
|
|
All channels ranging from 193.1625 THz to 195 THz will have their power equalized to -20 + 3 = -17 dBm (total power signal + noise).
|
|
|
|
Note that first carrier of the second partition has center frequency 193.1625 THz (its spectrum occupation ranges from 193.125 THz to 193.2 THz).
|
|
The last carrier of the second partition has center frequency 193.1 THz and spectrum occupation ranges from 193.075 THz to 193.125 THz.
|
|
There is no overlap of the occupation and both share the same boundary.
|
|
|
|
.. _equalization:
|
|
|
|
Equalization choices
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
ROADMs typically equalize the optical power across multiple channels using one of the available equalization strategies — either targeting a specific output power, or a specific power spectral density (PSD), or a spectfic power spectral density using slot_width as spectrum width reference (PSW).
|
|
All of these strategies can be adjusted by a per-channel power offset.
|
|
The equalization strategy can be defined globally per a ROADM model, or per each ROADM instance in the topology, and within a ROADM also on a per-degree basis.
|
|
|
|
Let's consider some example for the equalization. Suppose that the types of signal to be propagated are the following:
|
|
|
|
.. code-block:: json
|
|
|
|
{
|
|
"baud_rate": 32e9,
|
|
"f_min":191.3e12,
|
|
"f_max":192.3e12,
|
|
"spacing": 50e9,
|
|
"label": 1
|
|
},
|
|
{
|
|
"baud_rate": 64e9,
|
|
"f_min":193.3e12,
|
|
"f_max":194.3e12,
|
|
"spacing": 75e9,
|
|
"label": 2
|
|
}
|
|
|
|
|
|
with the PSD equalization in a ROADM:
|
|
|
|
.. code-block:: json
|
|
|
|
{
|
|
"uid": "roadm A",
|
|
"type": "Roadm",
|
|
"params": {
|
|
"target_psd_out_mWperGHz": 3.125e-4,
|
|
}
|
|
},
|
|
|
|
|
|
This means that power out of the ROADM will be computed as 3.125e-4 * 32 = 0.01 mW ie -20 dBm for label 1 types of carriers
|
|
and 3.125e4 * 64 = 0.02 mW ie -16.99 dBm for label2 channels. So a ratio of ~ 3 dB between target powers for these carriers.
|
|
|
|
With the PSW equalization:
|
|
|
|
.. code-block:: json
|
|
|
|
{
|
|
"uid": "roadm A",
|
|
"type": "Roadm",
|
|
"params": {
|
|
"target_out_mWperSlotWidth": 2.0e-4,
|
|
}
|
|
},
|
|
|
|
the power out of the ROADM will be computed as 2.0e-4 * 50 = 0.01 mW ie -20 dBm for label 1 types of carriers
|
|
and 2.0e4 * 75 = 0.015 mW ie -18.24 dBm for label2 channels. So a ratio of ~ 1.76 dB between target powers for these carriers.
|