This simulator explores a dense-channel optical link with two fiber spans and a mid-span erbium-doped amplifier. Choose the channel count and spacing, then change launch power, span length, requested gain, the amplifier output limit and the noise-figure parameter to see received power per channel, applied gain and optical signal-to-noise ratio.
• A 3D link with a DWDM transponder bank, a dense-channel multiplexer, a first transmission span, a pump diode and wavelength coupler, erbium-doped gain fiber with isolators, a second span, a demultiplexer and receiver bank, and an optical spectrum and power monitor. • Nine controls: channel count, spacing, launch power, span length, requested gain, output power limit, noise-figure parameter, pump enable and markers. • Ten readouts including applied gain, signal power into and out of the amplifier, received signal per channel, received OSNR, added ASE, margin against −25 dBm and first and last channel wavelengths. • Four guided experiments, a verification bench, Curves & measurements and a Learn & assess tab.
Channels sit on an optical frequency grid, fj = 193.1 THz + (j − N/2)Δf, with wavelengths from 299792.458/fj. Each span loses 0.2 dB/km, and the multiplexer and demultiplexer each lose 3 dB. The input OSNR is 45 dB in a 12.5 GHz reference bandwidth. The amplifier adds spontaneous emission with the approximate law PASE(B) = F·hν·(G − 1)·B where F = 10^(NF/10).
Applied gain is limited so that signals plus the modeled noise band stay within the output power cap, which is why sharing a capped amplifier among more channels reduces gain. OSNR is signal over amplified input noise plus ASE, and later passive loss attenuates signal and noise equally.
The model has equal-power channels on a frequency grid, ideal mux and demux routing, two uniform spans, an approximate amplifier ASE law, a fixed 45 dB input OSNR and a common gain cap. There is no pump-rate solution, gain ripple, gain transients, nonlinear fiber effects, chromatic dispersion or receiver BER. Pump-off is an ideal bypass and all powers are steady envelopes. Power margin and OSNR answer different questions, and the simulator reports both.
No. It amplifies signal and noise together and adds amplified spontaneous emission, so OSNR is lowered even as power is restored. Only electrical regeneration retimes and reshapes bits.
The amplifier has a total output power limit. More channels share that power, so the applied gain falls below the requested gain to keep the total within the cap.
Optical signal-to-noise ratio compares signal power with noise power in a 12.5 GHz reference bandwidth. It indicates signal quality, while the received-power margin indicates whether enough light arrives.
Gain is 0 dB and no new ASE is added, so received signal power falls. The assigned input OSNR is preserved by the passive loss.