Method of WDM channel tagging and monitoring, and apparatus

Abstract

Provided is an optical apparatus and method wherein power transfer coefficients arising from SRS are measured at a designated co-location point and the power of dithers, which are impressed on the channels of a multiplexed optical signal propagating through the optical apparatus, is measured at each co-location point. Within the optical apparatus distances between co-location points are short and the power transfer coefficients are effectively constant. Consequently, the power of each channel of the multiplexed optical signal at the co-location points is obtained from the power of the dithers at a respective one of the co-location points and the power transfer coefficients measured at the designated co-location point. In some embodiments, information on the channel power at the co-location points is used to provide instructions for compensating for fluctuations in channel power and / or channel count at an input and / or channel count within the optical apparatus.

Description

RELATED APPLICATION [0001] This application is a divisional of U.S. application Ser. No. 10 / 067,910 filed Feb. 8, 2002 and claims the benefit thereof.FIELD OF THE INVENTION [0002] The invention relates to the field of optical networks. More specifically the invention pertains to wavelength division multiplexed systems. BACKGROUND OF THE INVENTION [0003] Performance monitoring to determine channel presence and per-channel power has been employed using detection of an entire spectrum of channels of an optical signal wherein each channel has had impressed upon it a known dither. The dither can be implemented in many ways, such as amplitude modulation (AM) of a tone or set of tones or a code division multiple access (CDMA) modulation scheme, etc. [0004] In an example using AM detection each channel of a multiplexed optical signal has impressed upon it a unique AM tone and power of each channel of the optical signal is measured through differentiation of the unique AM tones and knowledge...

AI Technical Summary

Benefits of technology

[0023] The invention enables a well known and widely implemented dithered channel tagging and monitoring technique to be applied to WDM systems that would normally be hampered by SRS. The result is a simpler, faster, less expensive and more reliable monitoring system.

[0024] In addition, the invention enables the measurement of the SRS present in the system. Since SRS can affect system performance, information on the SRS can be used to control the system in such a way as to minimize the impact of the SRS.

Problems solved by technology

The accuracy of this method in estimating per channel power is limited by effects such as stimulated Raman scattering (SRS) which limits its usage to systems with a small number of spans, small channel counts and low per channel powers.

Modern systems are striving to achieve greater span, higher channel count and require higher channel power, thus limiting the applicability of this approach.

However, in the past, OSAs have not been equipped with the capability of discerning WID information.

In addition, it is usually much more expensive to implement, slower in taking measurements and the optical switch can limit the overall reliability of the OSA function.

Furthermore, an OSA takes up more space than a PIN detector and measurements at a plurality of co-location points using one or more OSAs causes fiber routing and handling issues.

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