Tektronix, Inc.

William A Trent

Florian Gene Bell

Mark D Marineau

Richard I Lane

Kevin B McDonald

Michael S Overton

Jeffrey H Goll

Glenn Bateman

Alexander R Lopez

A wide dynamic range optical receiver has low and high sensitivity signal channels for converting first and second portions of an optical input signal into voltage values representative of the various portions of the optical input signal. The voltage signals are converted into digital values by a converting means and a reconstruction is performed in a combining means to produce a digital output representative of the optical input signal. The wide dynamic range optical receiver may be used in an optical signal measurement instrument, such as an optical time domain reflectometer, where the optical return signal from a fiber under test is coupled to the wide dynamic range optical receiver in first and second portions with the first portion having an optical power level substantially less than the second portion.

Optical signal measurement instrument and wide dynamic range optical

An address generator that provides equivalent time sampling for a time domain reflectometer generates read and write addesses for simultaneous application to an aquisition memory over an address bus. For each iteration of a repetitive input signal an excitation pulse is delayed by an amount, dt, that is an integer submultiple of a sampling period, T. Read addresses for each iteration of the repetitive input signal start from an initial address and increment by T/dt for each data sample. Corresponding write addresses are generated from the read addresses one sample time later so that the address on the address bus has a read address that is one address ahead of the write address. The acquisition memory reads out data from the read address for accumulation with corresponding sampled data while accumulated data is being input to the write address.

Address generator for high speed data averager

An input signal is sampled by alternately coupling the input signal and a reference level to a sample storage element, whereby the magnitude of the signal stored by the storage element immediately following application of the input signal to the storage element is a function of the input signal magnitude and the magnitude of the signal stored by the storage element immediately preceding coupling of the input signal to the storage element is a function of the reference level.

Method of calibrating and controlling the optical power output of an OTDR

Sample and hold with intermediate reset voltage outside of the magnitude

An automatic masking system is used in an optical time domain reflectometer for implementing a method of compensating for relaxation transients in an optical receiver in the OTDR. The masking system drives an optical modulator that masks the optical reciver from high amplitude optical pulses in the return reflected light from a fiber under test. A masking pattern corresponding to the high amplitude optical pulses is generated from a first acquisition of data with the receiver unmasked from the return reflected light. The masking pattern is stored and used for generating a signal from the masking system to the optical modulator for blocking the high amplitude optical pulses in the return reflected light during a subsequent acquisition of data. In a third acquisition of data of the return reflected light, the optical modulator masks the receiver from the return reflected light. Combining the acquired data of the blocked return reflected light with the acquired data with the high amplitude optical pulses blocked, produces an output free of relaxation transients produced by the receiver. Combining the high amplitude optical pulse data from the first acquisition with the output from the subtracted acquisitions produces an output representative of the return reflected light.

Signal acquisition method and automatic masking system for an OTDR

A digital time base with differential period delay uses the difference in period between a master oscillator and a voltage controlled oscillator phase-locked to the master oscillator to achieve small time delay increments. The oscillators are used to drive respective delay generator trigger channels that have programmable counters and state machines. A first programmable counter is a clock counter to generate a lock signal to initiate a delay sequence, the lock signals from the respective channels being input to a phase detector to generate an error signal to keep the VCO phase-locked with the master oscillator. A second programmable counter is a delay counter that is controlled by a delay state machine to generate a delay signal. The delay signal is input to respective trigger state machines to generate the desired trigger signals, the duration of the trigger signals being a function of a third programmable counter. By programming the proper values for each counter, the amount of delay for each trigger signal may be controlled with respect to the other.

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Bend, OR, United States of America

William A Trent