Management of lumped losses along a fiber span

The lumped losses are used in the computation of the loss/gain profile
through the fiber whether the Raman effect is considered or not. The
computed power profile is used to calculate the related NLI impairment.

Using the 'gn_model_analytic' method, the lumped losses are taken into
account as the contribution of an additional total loss at the end of
the fiber span. In case the 'ggn_spectrally_separated' is selected, the
method uses the computed power profile according to the specified z and
frequency arrays. The lumped losses are so considered within the NLI
power evolution along the fiber.

Change-Id: I73a6baa321aca4d041cafa180f47afed824ce267
Signed-off-by: Jan Kundrát <jan.kundrat@telecominfraproject.com>

gnpy/core/parameters.py

@@ -156,6 +156,7 @@ class FiberParams(Parameters):
             else:
                 self._loss_coef = asarray(kwargs['loss_coef']) * 1e-3  # lineic loss dB/m
                 self._f_loss_ref = asarray(self._ref_frequency)  # Hz
+            self._lumped_losses = kwargs['lumped_losses'] if 'lumped_losses' in kwargs else []
         except KeyError as e:
             raise ParametersError(f'Fiber configurations json must include {e}. Configuration: {kwargs}')
 
@@ -188,6 +189,10 @@ class FiberParams(Parameters):
     def con_out(self):
         return self._con_out
 
+    @property
+    def lumped_losses(self):
+        return self._lumped_losses
+
     @con_out.setter
     def con_out(self, con_out):
         self._con_out = con_out
@@ -240,6 +245,8 @@ class FiberParams(Parameters):
         dictionary = super().asdict()
         dictionary['loss_coef'] = self.loss_coef * 1e3
         dictionary['length_units'] = 'm'
+        if not self.lumped_losses:
+            dictionary.pop('lumped_losses')
         if not self.raman_efficiency:
             dictionary.pop('raman_efficiency')
         return dictionary