Alphion Corporation

Tellium, Inc.

Paul Grabbe

Bharat P Dave

Robert R Cordell

Edward Ryszard Sokolowski

Murali Sampath

James John Ringo

In a fiber-optic communications system, a backup or redundant optical link is provided at the central office in parallel with the primary one in use. Parameters associated with the backup link, including its signal delay, its attenuation, etc. are stored at the time of installation. Upon failure of the primary link, switchover can be automatic, and the stored parameters are used to make adjustments necessary for the differences between the primary link and the backup link. In addition, having information on the differences between the two links, the central office is able to send control information downstream which is used at the remote site to control changes that must be made for upstream signals. For example, customer equipment can be signaled to adjust its timing for the next time slot or interface amplifiers can be adjusted to account for the change in attenuation. The central office could be provided with a corrected interface to accommodate the new link and a substantial buffer to account for the change in timing, and switchover to the new timing could be done gracefully.

Apparatus and method for ensuring continuity of fiber optic

A multi-wavelength optical receiver including multiple photodetectors receiving different ones of a multi-wavelength signal. For each wavelength-dedicated photodetector, a separate electronic receiver circuitry is provided including a current-to-voltage converting input transistor and an emitter-follower output transistor arranged as an operational amplifier with a feedback resistor. The circuit is improved by a cascode connection to the input transistor, by a reference to an analog ground rather than to a power supply line in both the photodiode and the cascode transistor, by the addition of capacitive shunts and a clamping transistor parallel to the feedback resistor in the feedback loop from the output transistor to the input transistor, by including positive and negative power supplies for the input and the output stages, by including multiple emitter followers in the output, by use of a differential second stage referenced to the analog ground, and by use of an output matching network that makes use of parasitic packaging inductances. Thereby, noise is reduce and inter-channel interference is minimized.

Optical receiver particularly useful for a multi-wavelength receiver array

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Tinton Falls, NJ, United States of America

Paul Grabbe