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Operation of optical modulators

An optical modulator and modulator technology, applied in instrumentation, optics, nonlinear optics, etc., can solve problems such as deteriorating large amounts of data, performance limitations, etc.

Inactive Publication Date: 2003-12-24
TELEFON AB LM ERICSSON (PUBL) +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In digital communication networks, such as those operating with the Synchronous Digital Hierarchy (SDH) format, there are severe limitations on performance
Especially in high bit rate systems, as might typically be used with this type of internal optical modulator, resetting the system may unacceptably corrupt large amounts of data

Method used

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  • Operation of optical modulators
  • Operation of optical modulators
  • Operation of optical modulators

Examples

Experimental program
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Embodiment Construction

[0043] see figure 1 , shows a laser 2 driven to produce a continuous optical output 4 coupled to an optical input 6 of an optical modulator 8 via an electrical fiber 10 . The fiber 10 polarization is maintained to ensure that the light entering the modulator 8 is of known polarization. The optical modulator is of the lithium niobate Mach Zehnder type which produces a dimmed output at the optical output 12 in response to an electrical signal Vmod applied to the control input 14 .

[0044] The modulator 8 has a periodic and generally sinusoidal waveform of light attenuation versus voltage Vmod response. It will be appreciated that the invention is also applicable to other types of optical modulators having a different optical response, provided that the response is periodic and the voltage corresponding to a cycle is known.

[0045] Electrical signal Vmod is generated by a driver circuit 16 in response to data applied to input 18 . The dimmed light appearing at the light outp...

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Abstract

The invention depicts a method and apparatus of operating an optical modulator. The optical modulator (8) having a cyclic optical attenuation versus voltage response,includes an input (34) to which the application of a bias voltage (v bias ) moves the modulator's response along the voltage axis to maintain the desired modulator's response. The apparatus includes bias voltage generator (32) which generates bias voltage v bias comprising the sum of first v fixed and second v var components. During normal operation, v fixed is set to correspond to the expected bias voltage required to maintain the desired modulator's response. The apparatus further comprises means (28, 30) for detecting the modulator's response and adjusting v var to maintain the desired response. Additionally the apparatus includes means (42) for detecting when V bias approaches the bias voltage limit; means (36) for adjusting v fixed to equal to the sum of the bias voltage and a voltage corresponding to one or more half cycles of the modulator's response; and means (38) for zeroing the voltage component v var.

Description

technical field [0001] The present invention relates to the operation of an optical modulator, in particular but not exclusively to the operation of a Mach Zehnder type optical modulator operating in an optical communication network in Synchronous Digital Hierarchy (SDH) format. Background technique [0002] In optical communication networks, data is sent in the form of light pulses, the presence of light pulses representing a logic state "1" and the absence of pulses or pulses of different values ​​representing a logic state "0". In low data rate systems, it is known to generate light pulses by driving a solid-state laser with the data to be transmitted. But these lasers "chirp"; that is, they no longer generate pulses of light at a single wavelength. This spread of optical wavelengths leads to pulse scattering as they travel down the fiber, which can ultimately limit the operating frequency and / or range of the optical network. [0003] It is known to operate the laser co...

Claims

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Application Information

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IPC IPC(8): G02F1/03G02F1/01H04B10/00H04B10/155
CPCG02F1/0123H04B10/50575H04B10/505
Inventor H·R·克拉玲本P·A·卡兰
Owner TELEFON AB LM ERICSSON (PUBL)