Need to have Inter stage loss between two stages of Dual Stage Amp.

[akhil-mutike]

Hi Team, i have observed that one cannot have a inter stage loss in dual stage amp in present form of Equipment Config. It is needed in case of Raman + EDFA , where there is some loss associated while Raman pump signal insertion. What do you think Team? @EstherLerouzic

[EstherLerouzic]

Dear @akhil-mutike,
You can model a dual stage amplifier with individual amplifiers and a midstage loss instead of using the predefined type variable_gain or dual_stage. You may use the "Fused" element type to model a loss midstage, or a voa_in value in the last amp. In the case of Raman amplification modelled with fixed gain localized amplifier with negative noise figure (not with RamanFiber), you can build a dual_stage amplifier like this one:

{
      "type_variety": "4pumps_raman",
      "type_def": "fixed_gain",
      "gain_flatmax": 12,
      "gain_min": 12,
      "p_max": 21,
      "nf0": -1,
      "allowed_for_design": false
    }, {
      "type_variety": "std_low_gain",
      "type_def": "variable_gain",
      "gain_flatmax": 16,
      "gain_min": 8,
      "p_max": 23,
      "nf_min": 6.5,
      "nf_max": 11,
      "out_voa_auto": false,
      "allowed_for_design": true
    }, {
      "type_variety": "hybrid_4pumps_lowgain",
      "type_def": "dual_stage",
      "raman": true,
      "gain_min": 25,
      "preamp_variety": "4pumps_raman",
      "booster_variety": "std_low_gain",
      "allowed_for_design": true
    },

and set the total gain of the amplifier instance with a value that accounts for this additional loss.  

               Fiber - LumpedRamanAmp - Loss - Edfa
Loss(dB)        25                         3
Gain(dB)                 12                     16
Power(dBm) 0                                         0

{
      "uid": "Span1",  "type": "Fiber", "type_variety": "SSMF", "params": { "length": 100, "loss_coef": 0.25}
}, {
      "uid": "Edfa1", "type": "Edfa", "type_variety": "hybrid_4pumps_lowgain", "operational": 
          {"gain_target": 28, "in_voa": 3, "delta_p": 0}
}