In the G.652 and LEAF optical fiber system, isolation bands need to be set when super 100G and 10G are mixed.

Question

Options

• ATrue
• BFalse

• A
  73% (24)
• B
  27% (9)

Explanation

Option A is correct because in G.652 (standard SMF) and LEAF (Large Effective Area Fiber) systems, mixing super 100G (e.g., DP-QPSK coherent signals) with legacy 10G (OOK-modulated) channels creates nonlinear interference issues. The narrowband, high-power 10G channels generate cross-phase modulation (XPM) and four-wave mixing (FWM) that degrade the phase-sensitive 100G+ coherent signals. Isolation bands - guard channels or spectral gaps - are inserted between the two channel groups to reduce this cross-technology nonlinear crosstalk to acceptable levels.

Option B is wrong because omitting isolation bands in a mixed-speed system on these fiber types leads to unacceptable OSNR penalties and BER degradation on the coherent 100G channels, making co-propagation without spectral separation impractical in real deployments.

Memory tip: Think of 10G and 100G channels as incompatible neighbors - the 10G signals are "loud and blunt" (high power, simple modulation) while 100G signals are "quiet and precise" (phase-sensitive coherent). You need a buffer zone (isolation band) between them, just like soundproofing between noisy and quiet rooms. If the fiber type is G.652 or LEAF and speeds are mixed → isolation band = mandatory.

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