Jds Uniphase Corporation

Other

United Technologies Corporation

Joseph P Farina

Gregory J McBrien

Wenyan Jiang

John D Borla

A method of controlling the operating parameters of an optical modulator, without using a dither signal, is provided. Past operating parameters are compared to present operating parameters using a quality of modulation signal obtained by cross-correlating the data modulation signal used to drive the optical modulator with the modulated optical signal output from the optical modulator. The quality of modulation signal is used to optimize the operating parameters (e.g., bias point) of the optical modulator, or other operating parameters of the arrangement, such as the modulator drive level, timing alignment, etc.

Ditherless optical modulator control

The invention relates to RF termination for reducing electrical signal reflections at the end of transmission line electrodes on an electro-optical (EO) optical modulator. The disclosed termination incorporates a RF tap which permits the monitoring of the RF power and reflection conditions at the EO modulator. The integrated termination/tap can also be integrated with detection circuitry, such as RF diodes and passive components, giving improved performance, lower cost manufacturability as well as a more compact and efficient package.

Integrated termination for EO modulator with RF signal monitoring functionality

An optical transmitter architecture has a return-to-zero (RZ) laser modulator coupled in cascade with a non-return-to-zero (NRZ) laser modulator. Modulator bias and electronic phase delay bias are controlled using dither-based feedback, so as to align the phase of the RZ clock signal with that of the NRZ data. A first method uses an RZ quadrature AM dither or an RZ 'hillclimber' bias dither, to apply a relatively low frequency dither signal to a variable RF delay for the RZ clock signal applied to the RZ modulator or NRZ data signal applied to the NRZ modulator. A second method is an RZ quadrature AM dither or 'hillclimber' bias dither scheme that applies equal amplitude and opposite phase dither signals to perform complementary modulation of both the RZ and NRZ MZ modulators simultaneously.

Cascaded RZ and NRZ laser modulators having RZ/NRZ phase alignment bias control

A sine wave locked in phase and frequency to a carrier having a high second harmonic content, carrying information on the magnitude of a parameter, is applied to an open loop operational amplifier which provides a trapezoidal waveform to a high speed, differential transistor pair which provides a pair of squarewave signals whose duty cycles are regulated by varying the threshold at which the differential pair switches. The squarewaves may be used as a second-harmonic-free demodualting signal. The fundamental premise is that if the amplitude levels of the squarewave levels of the squarewave are known to a high degree of accuracy, and they are equal in the positive and negative directions, then the average value is zero only for a 50% duty cycle. A current regulator generates a selected current to a constant value with a high gain amplifier. This current is switched from one side to the other of the differential pair by the trapezoidal waveform. The voltage excursions may be controlled in equal amounts above and below zero by selecting the resistive values in the collector circuits of the differential pair to be of a magnitude which will accomplish that end. The average value of the resulting squarewave is regulated to zero by integrating the voltage at the output of one of the collectors of the differential pair and varying the threshold at the base of the other transistor to obtain a 50% duty cycle.

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Southwick, MA, United States of America

Joseph P Farina