In the early stage of the project, the commissioning of the coherent system can properly improve the performance by increasing the transmitted optical power.

Question

Options

• ATrue
• BFalse

• A
  24% (5)
• B
  76% (16)

Explanation

Increasing transmitted optical power does not reliably improve performance in coherent optical systems, making the statement false. Unlike direct-detection systems where more signal power directly boosts SNR, coherent systems are highly sensitive to fiber nonlinearities (SPM, XPM, FWM) that grow with launch power and cannot be fully compensated by DSP. Blindly increasing power during early commissioning can therefore push the system past its optimal launch power, worsening BER rather than improving it. Option A (True) is wrong because it assumes a simple linear benefit from higher power, ignoring that coherent system performance follows an inverted-U curve versus launch power - improving then degrading.

Memory tip: Think of coherent systems as having a "Goldilocks" launch power - too low means poor OSNR, too high means nonlinear penalty. Early commissioning problems in coherent links are solved by proper alignment, DSP configuration, and OSNR optimization, not by simply turning up the power.

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