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Clock recovery for optical transmission systems

An optical communication system and clock technology, applied in the field of receivers, can solve the problems of difficulty, impossibility, and inability to start operation of the receiver of an optical transmission system.

Active Publication Date: 2015-02-11
CISCO TECH INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0023] Actuation of optical transmission system receivers may be difficult or impossible
clock recovery and compensation systems are interdependent and one cannot begin to operate without the other in at least a partially operational state

Method used

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  • Clock recovery for optical transmission systems
  • Clock recovery for optical transmission systems
  • Clock recovery for optical transmission systems

Examples

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Embodiment Construction

[0082] Embodiments of the present invention are described below by way of example only. These examples represent the best mode currently known to applicants to put the invention into practice, although they are not the only way in which the invention can be practiced. This description gives the functionality of the example and the sequence of steps used to build and operate the example. However, the same or equivalent functions and sequences can be implemented by different examples.

[0083] The 40Gbit / s DP-QPSK transmission system is used as the basis for the following description, but the described techniques can be applied to various transmission formats and rates without troublesome modifications.

[0084] Figure 10 A block diagram of a clock recovery system using a feedback loop 90 and a feedforward path 91 is shown. The phase detector 92 detects the phase of the output of the equalizer 74 . The output of phase detector 92 is fed back to voltage controlled oscillator...

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Abstract

A receiver for an optical communications system which corrects distortion of a received signal. A clock recovery system utilising a feedback and feedforward system are provided. The feedback loop comprises a phase detector and a clock source, while the feedforward loop comprises the phase detector and a delay element for delaying the output of distortion correction system. The feedback loop has a significantly lower bandwidth than the feedforward path. There are also provided methods of optimising tap weights and of acquiring initial tap weights.

Description

technical field [0001] The present invention relates to receivers for use in optical communication systems, and more particularly to clock recovery in dual-polarization quadrature phase-shift keying systems. Background technique [0002] Two basic forms of modulation are used in optical communication systems: amplitude shift keying (ASK) and phase shift keying (PSK), which encode data in the amplitude and phase of the emitted light, respectively. The direct detection method can be used to detect and receive ASK signals instead of PSK signals in which the data cannot be recovered from the power envelope of the light. Coherent detection, where received light is mixed with an optical local oscillator (LO), enables reception of PSK signals. [0003] The optical LO can be locked to the frequency and phase of the input optical signal (homodyne reception), or can be kept very close but not precisely locked to the input optical signal (intradyne reception), or can be at a location ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B10/61
CPCH04B10/611H04L25/03057H04B10/614H04B10/6165H04B10/61H04B10/65H04L7/0331H04L7/0338
Inventor 克里斯托弗·佛路德格
Owner CISCO TECH INC
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