The use of QPSK modulation can reduce OSNR requirements and fiber nonlinear hazards, improve dispersion tolerance PMD tolerance, etc.

Question

Options

• ATrue
• BFalse

• A
  77% (17)
• B
  23% (5)

Explanation

Option A is correct because QPSK (Quadrature Phase Shift Keying), particularly with coherent detection, offers several tangible advantages in optical fiber links. By encoding 2 bits per symbol across four phase states rather than relying on amplitude, QPSK achieves better optical signal-to-noise ratio (OSNR) sensitivity and is inherently more resistant to fiber nonlinearities (such as self-phase modulation and cross-phase modulation) than higher-order formats like 16-QAM or 64-QAM, which require tighter signal constellations and higher OSNR margins. Coherent QPSK also enables powerful digital signal processing (DSP) at the receiver, which can compensate for chromatic dispersion (CD) and polarization mode dispersion (PMD) electronically - greatly relaxing physical layer tolerances. There is no meaningful "distractor" here since this is a True/False question - the false option (B) would be wrong because all four claimed benefits (reduced OSNR requirements, reduced nonlinear penalty, improved dispersion tolerance, improved PMD tolerance) are well-established characteristics of coherent QPSK systems.

Memory tip: Think of QPSK as the "sweet spot" modulation - it uses phase (not amplitude) to carry data, making it tough against noise and fiber impairments, unlike higher-order QAM formats that demand cleaner, more tightly controlled signals. "Q = Quite resilient."

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