Optical attenuator

Abstract

A method of generating a pulse width modulated (PWM) signal comprises: receiving digital demand data V>control< comprising at least one more significant bit (bit>7< to bit 14>) and at least one less significant bit (bit0 to bit6). The PWM signal comprises a sequence of one or more frames (100), each frame: comprising a plurality of PWM pulses (W1 to W127) whose duty cycle is substantially governed by the at least one more significant bit (bit7 to bit14); and having at least one of its PWM pulses selected to have its duty cycle modified in response to the at least one less significant bit (bit0 to bit6); each of the at least one less significant bit (bit0 to bit6) uniquely mapping onto the at least one selected PWM pulse of the frame (100). The invention is also concerned with apparatus operable according to the above method and an optical attenuator whose optical attenuation is dependent upon its temperature and in which the temperature an hence attenuation is controlled using the above PWM signal.

Description

This application is a divisional application of the following international invention patent application submitted on March 23, 2001, international application number: PCT / GB01 / 01309, national application number: 01807041.8, invention name: "Method for generating pulse width modulation signal and devices and optical attenuators controlled by pulse width modulated signals” technical field The present invention relates to a method and apparatus for generating a pulse width modulated (PWM) signal. More specifically, the present invention relates to temperature control of electro-optical components, such as attenuators, filters, and solid-state lasers. These elements are used in optical communication systems. Also, although not exclusively, the present invention generally relates to an optical attenuator with enhanced resolution for use in an optical communication system. Background technique In traditional optical communication systems, optical attenuators are used to adjus...

AI Technical Summary

Problems solved by technology

The disadvantage of this circuit is that the power dissipation in the power tube is close to that of the associated thermoelectric element

The traditional way to increase the PWM resolution is to use a higher master clock frequency f clk ; This method will drastically increase the cost of the corresponding digital circuit and increase the operating power consumption of the circuit

Moreover, in practical applications, the clock frequency that digital circuits can achieve is limited.

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