For a system with an optical amplifier, the upper threshold of the received optical power of the wavelength division side of the OTU single board and the line single board (APD type receiving laser)…

Question

Options

• ATrue
• BFalse

• A
  74% (37)
• B
  26% (13)

Explanation

Option A is correct because in amplified optical systems, the upper power threshold for APD-type receivers on OTU line boards is intentionally set 3 dB below the module's overload point, providing a standard safety margin that prevents the APD from saturating or sustaining damage from excessive optical power. The -3 dB offset (equivalent to halving the linear power level) is a defined engineering specification in optical transport standards, accounting for power variability introduced by optical amplifiers such as EDFAs. Since optical amplifiers can boost signal levels significantly, this guardrail ensures the received power stays within the APD's safe operating range even under worst-case amplifier conditions. Option B (False) is incorrect because it contradicts this established threshold specification - there is no alternative standard that places the upper limit at any other offset from the overload point for this configuration.

Memory tip: Think of the -3 dB rule as a "half-power safety cushion" - APD receivers are sensitive devices, so the system keeps the upper power limit at exactly half the overload power to stay comfortably in the safe zone. If you remember "amplifiers → more power risk → -3 dB headroom below overload," you'll lock in the answer.

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