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In the book Nonlinear Optics, it is stated that the nonlinear effects start to become a problem in WDM systems (around 1550 nm) after about 1 mW of optical power. However, I measured the optical power at transmission of a transmitting laser of a 10GBASE-ZR on a short, 2 km link, and found that it was 2.5 mW.

What is the operating optical power of telecommunications lasers? Does it differ for inter-continental links compared to short links, i.e. between buildings on a campus? If they are above 1 mW, are nonlinear effects a concern?

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  • $\begingroup$ Not sure if this is a question for physics or electrical engineering... $\endgroup$ – Catherine Holloway Jun 12 '12 at 16:52
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    $\begingroup$ Whether nonlinear effects are a problem depend on other things too besides average power! Single-mode vs multi-mode fiber, length of the link, CW versus short intense pulses, etc... $\endgroup$ – Steve Byrnes Jun 13 '12 at 3:58
  • $\begingroup$ To my limited knowledge, NL effects are a concern and manifest as pulse distortion (due to many competing effects). They are more pronounced when the pulse width is short (100ns perhaps?). This effectively puts a limit on useful bandwidth. I vaguely remember analysis using an eye-diagram to quantify the effect of distortion. $\endgroup$ – Antillar Maximus May 18 '13 at 23:01
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The common optical power on a 4km link is about 1mW, with ~2dB/km loss. with a good-quality single-mod fiber, the non-linear effects are negligible.

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