Update ietf-layer0-types.yang

Updated min-OSNR; added rx-ref-channel-power attribute and rx-channel-power-penalty: fix #66

- Addressed proposals 1-4 in ietf-ccamp-wg/draft-ietf-ccamp-optical-impairment-topology-yang#126

Co-Authored-By: sergio belotti <sergio.belotti@nokia.com>

ietf-layer0-types.yang

@@ -27,7 +27,7 @@ module ietf-layer0-types {
      Division Multiplexing) and DWDM (Dense Wavelength Division
      Multiplexing)) and flexi-grid optical networks.
 
-     Copyright (c) 2022 IETF Trust and the persons identified
+     Copyright (c) 2023 IETF Trust and the persons identified
      as authors of the code.  All rights reserved.
 
      Redistribution and use in source and binary forms, with
@@ -51,7 +51,7 @@ module ietf-layer0-types {
 
 // replace the revision date with the module publication date
 // the format is (year-month-day)
-  revision 2022-10-23 {
+  revision 2023-03-07 {
     description
       "To be updated";
     reference
@@ -1157,12 +1157,17 @@ module ietf-layer0-types {
        capabilities of a transceiver.";
 
     container supported-modes {
+      presence
+        "When present, it indicates that the modes supported by a 
+        transceiver are reported.";
       description
-        "Transceiver's supported modes.";
+        "The top level container for the list supported 
+        transceiver's modes.";
       list supported-mode {
         key "mode-id";
         config false;
-        description "list of supported transceiver's modes.";
+        min-elements 1;
+        description "The list of supported transceiver's modes.";
         leaf mode-id {
           type string { 
             length "1..255";
@@ -1362,13 +1367,39 @@ module ietf-layer0-types {
     }
     leaf min-OSNR {
       type snr;
+      units "dBm";
       config false;
-      description "min OSNR measured over 0.1 nm 
-      resolution bandwidth:
-      if received OSNR at minimum Rx-power is lower than MIN-OSNR,
-      an increased level of bit-errors post-FEC needs 
-      to be expected.";
-      // change resolution BW from 12.5 GHz to 0.1 nm
+      description
+        "min OSNR measured over 0.1 nm resolution bandwidth:
+        if received OSNR at Rx-power reference point
+        (rx-ref-channel-power) is lower than MIN-OSNR, an increased 
+        level of bit-errors post-FEC needs to be expected";
+    }
+    leaf rx-ref-channel-power {
+      type dbm-t;
+      config false;
+      description
+        "The channel power used as reference for defining penalties 
+        and min-OSNR";
+    }
+    list rx-channel-power-penalty {
+      config false;
+      description
+        "Optional penalty associated with a received power
+          lower than rx-ref-channel-power.
+          This list of pair power and penalty can be used to
+          sample the function penalty = f(rx-channel-power).";
+      leaf rx-channel-power {
+        type union {
+          type dbm-t;
+          type empty;
+        }
+        units "dBm";
+        config false;
+        mandatory true;
+        description "Received Power";
+      }
+      uses penalty-value;
     }
     leaf min-Q-factor {
       type int32;