Planning Fiber Optic Networks by Bob Chomycz

Author:Bob Chomycz [Chomycz, Bob]
Language: eng
Format: epub, pdf
Publisher: McGraw-Hill
Published: 2009-03-07T22:00:00+00:00

FIGURE 6.15 CWDM fiber spectrum.

Because of lower fiber attenuation at higher wavelengths and water peak attenuation, 8-channel CWDM multiplexers typically use channels 1471 to 1611 nm and 4-channel units use channels 1611 to 1551 nm, see Table C4 in App. C.

CWDM transceivers are significantly less expensive than DWDM transceivers. This can be attributed to the factors listed below:

1. CWDM transceivers use simpler laser designs without elaborate temperature stabilization circuitry to keep the laser from drifting out of the DWDM narrow channel passband (60 GHz). The CWDM wider channel passband (1600 GHz) allows for laser drift without costly laser cooling and control circuitry.

2. Because of the large CWDM channel passband, transceivers have less stringent laser center wavelength and spectral width tolerances.

3. CWDM lasers use lower cost directly modulated DFB and VCSEL technology.

The CWDM lower cost technology is ideal for increasing fiber capacity up to 18 channels in metro fiber applications (<80 km).

*Corning Incorporated trademark

†Furukawa Electric North America Inc. trademark

It should be noted that non-CWDM transceivers that are labeled 1310 or 1550 nm will likely not work in CWDM channels 1311 or 1551 nm because of their large laser drift and wide manufacturing tolerances. The 1310 and 1550 designation on these transceivers indicates only that their laser will operate in the 1310 or 1550 bands (O and C bands) and not necessarily at that specific wavelength or CWDM channel. CWDM passband is ± 6.5 nm and these transceiver lasers may not fall into this spectrum or may drift out of this spectrum. It is best to acquire transceivers that are designated CWDM when using this WDM technology.

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