Methods and apparatus for optical modulation amplitude measurement

Abstract

Techniques for measuring optical modulation amplitude (OMA) are disclosed. For example, a technique for measuring an OMA value associated with an input signal includes the following steps / operations. The input signal is applied to a photodetector, wherein the photodetector is calibrated to have a given responsivity value R, and further wherein the photodetector generates an output signal in response to the input signal. The output signal from the photodetector is applied to a radio frequency (RF) power meter, wherein the RF power meter measures the root mean squared (RMS) power value of the output signal received from the photodetector. The OMA value associated with the input signal is determined in response to the root mean squared (RMS) power value measured by the RF power meter. The OMA value may be determined as a function of a factor F derived from a relationship between an amplitude of a data signal and the RMS value of the data signal.

Description

FIELD OF THE INVENTION [0001] The present invention relates to optical network parameter measurement techniques and, more particularly, to techniques for measuring optical modulation amplitude. BACKGROUND OF THE INVENTION [0002] The Fibre Channel (FC) standards are an American National Standards Institute (ANSI) standards set that defines a common transport system for use with different protocols or applications. The initial core FC standard is identified as X.3230-1994-Fibre Channel Physical and Signaling Standard (FC-PH), the disclosure of which is incorporated by reference herein. [0003] Until recently, FC optical transceivers were specified with an acceptable range of optical receiver sensitivity and transmitter output measured in terms of average optical power at a minimum extinction ratio level. When an optical link failure occurred, fault determination procedures typically called for measurement of the average optical power at both transmit and receive ends of the link. If th...

AI Technical Summary

Benefits of technology

[0017] Accordingly, principles of the present invention provide techniques that enable measurement of OMA in a variety of settings and applications. For example, the inventive techniques may be used for field (e.g., customer location) measurement of OMA. Also, by way of further example, the inventive techniques may be used for optical component manufacturing measurements, which may lower costs through lower equipment costs and faster testing time.

Problems solved by technology

If the transceiver power levels were within specified limits, but the link continued to fail, then the problem was attributed to the optical cable plant.

If the link was delivering acceptable power levels and errors continued to occur, the failure was assumed to reside in the optical receiver.

This Standards change means that it is no longer possible to determine whether an optical transceiver is within specification simply by measuring the average optical power input to the receiver.

Such an approach is a ratio measurement of noise power to signal power and thus does not calibrate the photodetector to obtain a true OMA reading.

These methods and circuits do not and can not report a calibrated OMA.

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