Abstract

Monitoring the performance of optical networks is important in optical telecommunication industry. The performance of a DWDM optical communication network can be monitored by measuring the wavelengths, powers and signal-to-noise ratios of its channels in real-time. Diffraction grating and tunable filters are most commonly used techniques for DWDM network performance monitoring. Wavelength references are usually used to remove wavelength uncertainties associated with tunable filters. Fabry-Perot tunable filters with different wavelength reference techniques have been used in the past.^1,2 With tunable filters, it is potentially to obtain finer wavelength resolutions and to have tapped signals for Bit-Error-Rate Test (BERT). Because of uncertainties of mechanical scanning, real-time wavelength calibrations are commonly used to ensure the wavelength accuracy. Usually, optical-mechanical switches are used to switch back and forth between the optical signal channels under monitoring and the optical wavelength reference channel for referencing. Wavelength reference techniques can be a serial of Fiber Bragg Grating (FBG) filters or a slope filter. Gas cell wavelength references have also been used for DWDM applications. In those applications, gas cells covering the same wavelength as that the communication signal channel wavelengths are often used.³

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