diff --git a/gnpy/core/elements.py b/gnpy/core/elements.py
index 010e182f..bfdd4788 100644
--- a/gnpy/core/elements.py
+++ b/gnpy/core/elements.py
@@ -891,18 +891,23 @@ class Fiber(_Node):
 
         :return Dict[str, Any]: JSON representation of the fiber.
         """
+        params = {
+            # have to specify each because namedtupple cannot be updated :(
+            'length': round(self.params.length * 1e-3, 6),
+            'loss_coef': round(self.params.loss_coef * 1e3, 6),
+            'length_units': 'km',
+            'att_in': self.params.att_in,
+            'con_in': self.params.con_in,
+            'con_out': self.params.con_out
+        }
+        # Export pmd_coef only if it is not a default from library.
+        if self.params.pmd_coef_defined:
+            params['pmd_coef'] = self.params.pmd_coef
+
         return {'uid': self.uid,
                 'type': type(self).__name__,
                 'type_variety': self.type_variety,
-                'params': {
-                    # have to specify each because namedtupple cannot be updated :(
-                    'length': round(self.params.length * 1e-3, 6),
-                    'loss_coef': round(self.params.loss_coef * 1e3, 6),
-                    'length_units': 'km',
-                    'att_in': self.params.att_in,
-                    'con_in': self.params.con_in,
-                    'con_out': self.params.con_out
-                },
+                'params': params,
                 'metadata': {
                     'location': self.metadata['location']._asdict()
                 }
@@ -1025,7 +1030,7 @@ class Fiber(_Node):
             else:
                 wavelength = c / frequency
                 dispersion = self.params.dispersion + self.params.dispersion_slope * \
-                             (wavelength - c / self.params.f_dispersion_ref)
+                             (wavelength - c / self.params.f_dispersion_ref)  # noqa E127
         beta2 = -((c / frequency) ** 2 * dispersion) / (2 * pi * c)
         return beta2
 
@@ -1048,7 +1053,7 @@ class Fiber(_Node):
                 dispersion_slope = self.params.dispersion_slope
                 beta2 = self.beta2(frequency)
                 beta3 = (dispersion_slope - (4 * pi * frequency ** 3 / c ** 2) * beta2) / (
-                            2 * pi * frequency ** 2 / c) ** 2
+                            2 * pi * frequency ** 2 / c) ** 2  # noqa E127
         return beta3
 
     def gamma(self, frequency=None):
diff --git a/gnpy/core/parameters.py b/gnpy/core/parameters.py
index c96772e8..0269208b 100644
--- a/gnpy/core/parameters.py
+++ b/gnpy/core/parameters.py
@@ -343,6 +343,7 @@ class FiberParams(Parameters):
 
             # Polarization Mode Dispersion
             self._pmd_coef = kwargs['pmd_coef']  # s/sqrt(m)
+            self._pmd_coef_defined = kwargs.get('pmd_coef_defined', kwargs['pmd_coef'] is True)
 
             # Loss Coefficient
             if isinstance(kwargs['loss_coef'], dict):
@@ -428,6 +429,10 @@ class FiberParams(Parameters):
     def pmd_coef(self):
         return self._pmd_coef
 
+    @property
+    def pmd_coef_defined(self):
+        return self._pmd_coef_defined
+
     @property
     def ref_wavelength(self):
         return self._ref_wavelength
diff --git a/gnpy/core/utils.py b/gnpy/core/utils.py
index 4e7a7c33..463a532a 100644
--- a/gnpy/core/utils.py
+++ b/gnpy/core/utils.py
@@ -329,6 +329,35 @@ def merge_amplifier_restrictions(dict1, dict2):
     return copy_dict1
 
 
+def use_pmd_coef(dict1: dict, dict2: dict):
+    """If Fiber dict1 is missing the pmd_coef value then use the one of dict2.
+    In addition records in "pmd_coef_defined" key the pmd_coef if is was defined in dict1.
+
+    :param dict1: A dictionnary that contains "pmd_coef" key.
+    :type dict1: dict
+    :param dict2: Another dictionnary that contains "pmd_coef" key.
+    :type dict2: dict
+
+    >>> dict1 = {'a': 1, 'pmd_coef': 1.5e-15}
+    >>> dict2 = {'a': 2, 'pmd_coef': 2e-15}
+    >>> use_pmd_coef(dict1, dict2)
+    >>> dict1
+    {'a': 1, 'pmd_coef': 1.5e-15, 'pmd_coef_defined': True}
+
+    >>> dict1 = {'a': 1}
+    >>> use_pmd_coef(dict1, dict2)
+    >>> dict1
+    {'a': 1, 'pmd_coef_defined': False, 'pmd_coef': 2e-15}
+    """
+    if 'pmd_coef' in dict1 and not dict1['pmd_coef'] \
+            or ('pmd_coef' not in dict1 and 'pmd_coef' in dict2):
+        dict1['pmd_coef_defined'] = False
+        dict1['pmd_coef'] = dict2['pmd_coef']
+    elif 'pmd_coef' in dict1 and dict1['pmd_coef']:
+        dict1['pmd_coef_defined'] = True
+    # all other case do not need any change
+
+
 def silent_remove(this_list, elem):
     """Remove matching elements from a list without raising ValueError
 
@@ -558,3 +587,23 @@ def transform_data(data: str) -> Union[List[int], None]:
     if isinstance(data, str):
         return [int(x) for x in data.split(' | ')]
     return None
+
+
+def convert_pmd_lineic(pmd: Union[float, None], length: float, length_unit: str) -> Union[float, None]:
+    """Convert PMD value of the span in ps into pmd_lineic in s/sqrt(km)
+
+    :param pmd: value in ps
+    :type pmd: Union[float, None]
+    :param length: value in length_unit
+    :type length: float
+    :param length_unit: 'km' or 'm'
+    :type length_unit: str
+    :return: lineic PMD s/sqrt(m)
+    :rtype: Union[float, None]
+
+    >>> convert_pmd_lineic(10, 0.001, 'km')
+    1e-11
+    """
+    if pmd:
+        return pmd * 1e-12 / sqrt(convert_length(length, length_unit))
+    return None
diff --git a/gnpy/example-data/edfa_example_network.json b/gnpy/example-data/edfa_example_network.json
index 861be903..1a8ed91a 100644
--- a/gnpy/example-data/edfa_example_network.json
+++ b/gnpy/example-data/edfa_example_network.json
@@ -23,7 +23,8 @@
         "length_units": "km",
         "att_in": 0,
         "con_in": 0.5,
-        "con_out": 0.5
+        "con_out": 0.5,
+        "pmd_coef": 3.0e-15
       },
       "metadata": {
         "location": {
diff --git a/gnpy/example-data/meshTopologyExampleV2.xls b/gnpy/example-data/meshTopologyExampleV2.xls
index 0704900e..93ca00dc 100644
Binary files a/gnpy/example-data/meshTopologyExampleV2.xls and b/gnpy/example-data/meshTopologyExampleV2.xls differ
diff --git a/gnpy/tools/convert.py b/gnpy/tools/convert.py
index 0e6ed51e..d8df962f 100755
--- a/gnpy/tools/convert.py
+++ b/gnpy/tools/convert.py
@@ -33,7 +33,7 @@ from xlrd.sheet import Sheet
 from xlrd.biffh import XLRDError
 from networkx import DiGraph
 
-from gnpy.core.utils import silent_remove, transform_data
+from gnpy.core.utils import silent_remove, transform_data, convert_pmd_lineic
 from gnpy.core.exceptions import NetworkTopologyError
 from gnpy.core.elements import Edfa, Fused, Fiber
 
@@ -170,7 +170,7 @@ class Link:
         'east_lineic': 0.2,
         'east_con_in': None,
         'east_con_out': None,
-        'east_pmd': 0.1,
+        'east_pmd': None,
         'east_cable': ''
     }
 
@@ -636,6 +636,62 @@ def create_west_eqpt_element(node: Node, nodes_by_city: Dict[str, Node]) -> dict
     return eqpt
 
 
+def create_east_fiber_element(fiber: Node, nodes_by_city: Dict[str, Node]) -> Dict:
+    """Create fibers json elements for the east direction.
+
+    :param fiber: The Node object representing the equipment.
+    :type fiber: Node
+    :param nodes_by_city: A dictionary mapping city names to Node objects.
+    :type nodes_by_city: Dict[str, Node]
+    :return: A dictionary representing the west equipment element in JSON format.
+    :rtype: Dict
+    """
+    fiber_dict = {
+        'uid': f'fiber ({fiber.from_city} \u2192 {fiber.to_city})-{fiber.east_cable}',
+        'metadata': {'location': midpoint(nodes_by_city[fiber.from_city],
+                                          nodes_by_city[fiber.to_city])},
+        'type': 'Fiber',
+        'type_variety': fiber.east_fiber,
+        'params': {
+            'length': round(fiber.east_distance, 3),
+            'length_units': fiber.distance_units,
+            'loss_coef': fiber.east_lineic,
+            'con_in': fiber.east_con_in,
+            'con_out': fiber.east_con_out
+        }
+    }
+    if fiber.east_pmd:
+        fiber_dict['params']['pmd_coef'] = convert_pmd_lineic(fiber.east_pmd, fiber.east_distance, fiber.distance_units)
+    return fiber_dict
+
+
+def create_west_fiber_element(fiber: Node, nodes_by_city: Dict[str, Node]) -> Dict:
+    """Create fibers json elements for the west direction.
+
+    :param fiber: The Node object representing the equipment.
+    :type fiber: Node
+    :param nodes_by_city: A dictionary mapping city names to Node objects.
+    :type nodes_by_city: Dict[str, Node]
+    :return: A dictionary representing the west equipment element in JSON format.
+    :rtype: Dict
+    """
+    fiber_dict = {
+        'uid': f'fiber ({fiber.to_city} \u2192 {fiber.from_city})-{fiber.west_cable}',
+        'metadata': {'location': midpoint(nodes_by_city[fiber.from_city],
+                                          nodes_by_city[fiber.to_city])},
+        'type': 'Fiber',
+        'type_variety': fiber.west_fiber,
+        'params': {'length': round(fiber.west_distance, 3),
+                   'length_units': fiber.distance_units,
+                   'loss_coef': fiber.west_lineic,
+                   'con_in': fiber.west_con_in,
+                   'con_out': fiber.west_con_out}
+    }
+    if fiber.west_pmd:
+        fiber_dict['params']['pmd_coef'] = convert_pmd_lineic(fiber.west_pmd, fiber.west_distance, fiber.distance_units)
+    return fiber_dict
+
+
 def xls_to_json_data(input_filename: Path, filter_region: List[str] = None) -> dict:
     """Read the Excel sheets and produce the JSON dict in GNPy format (legacy).
 
@@ -698,29 +754,8 @@ def xls_to_json_data(input_filename: Path, filter_region: List[str] = None) -> d
                                           'longitude': x.longitude}},
                 'type': 'Fused'}
                for x in nodes_by_city.values() if x.node_type.lower() == 'fused']
-            + [{'uid': f'fiber ({x.from_city} \u2192 {x.to_city})-{x.east_cable}',
-                'metadata': {'location': midpoint(nodes_by_city[x.from_city],
-                                                  nodes_by_city[x.to_city])},
-                'type': 'Fiber',
-                'type_variety': x.east_fiber,
-                'params': {'length': round(x.east_distance, 3),
-                           'length_units': x.distance_units,
-                           'loss_coef': x.east_lineic,
-                           'con_in': x.east_con_in,
-                           'con_out': x.east_con_out}
-                }
-               for x in links]
-            + [{'uid': f'fiber ({x.to_city} \u2192 {x.from_city})-{x.west_cable}',
-                'metadata': {'location': midpoint(nodes_by_city[x.from_city],
-                                                  nodes_by_city[x.to_city])},
-                'type': 'Fiber',
-                'type_variety': x.west_fiber,
-                'params': {'length': round(x.west_distance, 3),
-                           'length_units': x.distance_units,
-                           'loss_coef': x.west_lineic,
-                           'con_in': x.west_con_in,
-                           'con_out': x.west_con_out}
-                } for x in links]
+            + [create_east_fiber_element(x, nodes_by_city) for x in links]
+            + [create_west_fiber_element(x, nodes_by_city) for x in links]
             + [{'uid': f'west edfa in {x.city}',
                 'metadata': {'location': {'city': x.city,
                                           'region': x.region,
diff --git a/gnpy/tools/json_io.py b/gnpy/tools/json_io.py
index f36e71cf..25d96439 100644
--- a/gnpy/tools/json_io.py
+++ b/gnpy/tools/json_io.py
@@ -23,7 +23,7 @@ from gnpy.core.equipment import trx_mode_params, find_type_variety
 from gnpy.core.exceptions import ConfigurationError, EquipmentConfigError, NetworkTopologyError, ServiceError
 from gnpy.core.science_utils import estimate_nf_model
 from gnpy.core.info import Carrier
-from gnpy.core.utils import automatic_nch, automatic_fmax, merge_amplifier_restrictions, dbm2watt
+from gnpy.core.utils import automatic_nch, automatic_fmax, merge_amplifier_restrictions, dbm2watt, use_pmd_coef
 from gnpy.core.parameters import DEFAULT_RAMAN_COEFFICIENT, EdfaParams, MultiBandParams, DEFAULT_EDFA_CONFIG
 from gnpy.topology.request import PathRequest, Disjunction, compute_spectrum_slot_vs_bandwidth, ResultElement
 from gnpy.topology.spectrum_assignment import mvalue_to_slots
@@ -687,6 +687,9 @@ def network_from_json(json_data: dict, equipment: dict) -> DiGraph:
                 if not extra_params:
                     msg = f'ROADM {el_config["uid"]}: invalid equalization settings'
                     raise ConfigurationError(msg)
+            # use temp pmd_coef if it exists else use the default one from library and keep this knowledge in
+            # pmd_coef_defined
+            use_pmd_coef(temp, extra_params)
             temp = merge_amplifier_restrictions(temp, extra_params)
             el_config['params'] = temp
             el_config['type_variety'] = variety
diff --git a/tests/invocation/spectrum1_transmission_main_example b/tests/invocation/spectrum1_transmission_main_example
index d38d3fe8..33ddb28d 100644
--- a/tests/invocation/spectrum1_transmission_main_example
+++ b/tests/invocation/spectrum1_transmission_main_example
@@ -101,7 +101,7 @@ Transceiver trx Lorient_KMA
   OSNR ASE (0.1nm, dB):      23.89
   OSNR ASE (signal bw, dB):  19.81
   CD (ps/nm):                2171.00
-  PMD (ps):                  0.46
+  PMD (ps):                  3.03
   PDL (dB):                  0.00
   Latency (ms):              0.64
   Actual pch out (dBm):      0.00
diff --git a/tests/invocation/spectrum2_transmission_main_example b/tests/invocation/spectrum2_transmission_main_example
index 727764d3..d21bd8da 100644
--- a/tests/invocation/spectrum2_transmission_main_example
+++ b/tests/invocation/spectrum2_transmission_main_example
@@ -101,7 +101,7 @@ Transceiver trx Lorient_KMA
   OSNR ASE (0.1nm, dB):      mode_1: 23.91, mode_2: 23.87
   OSNR ASE (signal bw, dB):  mode_1: 19.83, mode_2: 16.78
   CD (ps/nm):                2171.00
-  PMD (ps):                  0.46
+  PMD (ps):                  3.03
   PDL (dB):                  0.00
   Latency (ms):              0.64
   Actual pch out (dBm):      mode_1: 0.00, mode_2: 0.00
diff --git a/tests/invocation/transmission_main_example b/tests/invocation/transmission_main_example
index a6dc6e2c..fc4c542e 100644
--- a/tests/invocation/transmission_main_example
+++ b/tests/invocation/transmission_main_example
@@ -52,7 +52,7 @@ Transceiver Site_B
   OSNR ASE (0.1nm, dB):      33.30
   OSNR ASE (signal bw, dB):  29.21
   CD (ps/nm):                1336.00
-  PMD (ps):                  0.36
+  PMD (ps):                  0.85
   PDL (dB):                  0.00
   Latency (ms):              0.39
   Actual pch out (dBm):      0.00
diff --git a/tests/test_logger.py b/tests/test_logger.py
index 7e9f9064..3aff1f42 100644
--- a/tests/test_logger.py
+++ b/tests/test_logger.py
@@ -377,8 +377,8 @@ def wrong_element():
         "expected_msg": "Config error in fiber (ILA2 → ILA1): "
                         + "Fiber configurations json must include \'length_units\'. Configuration: "
                         + "{\'length\': 100.0, \'loss_coef\': 0.2, \'att_in\': 0, \'con_in\': 0, \'con_out\': 0, "
-                        + "\'type_variety\': \'SSMF\', \'dispersion\': 1.67e-05, \'effective_area\': 8.3e-11, "
-                        + "\'pmd_coef\': 1.265e-15}"
+                        + "\'pmd_coef_defined': False, \'pmd_coef\': 1.265e-15, "
+                        + "\'type_variety\': \'SSMF\', \'dispersion\': 1.67e-05, \'effective_area\': 8.3e-11}"
     })
     return data