Sampling Clock Phase Detection After Optical Spectral Narrowing

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Solution Overview

Problem

In optical transmission systems, spectral narrowing caused by multiple optical filters degrades signal quality and reduces sensitivity of sampling clock shift detection, leading to decreased jitter and wander tolerance, which affects the synchronization of sampling clocks and reception quality.

Innovation Solution

A sampling clock synchronizing apparatus that includes an A/D converter and a processor to compensate for spectral narrowing by using filter characteristics opposite to those of the narrowing, allowing for accurate detection and synchronization of sampling clock phase shifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If optical filters are used for wavelength demultiplexing and multiplexing in optical repeaters, then arbitrary wavelength channels can be inserted or branched, but spectral narrowing occurs which degrades signal quality and reduces detection sensitivity

Engineering Contradiction:

Improvewavelength channel insertion and branching capabilityVSAvoiddetection sensitivity of sampling clock phase shift

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

A sampling clock synchronizing apparatus is introduced as an intermediary device between the optical signal transmission path and the detection system. This apparatus includes a phase shift detection circuit that detects phase shifts in the sampling clock caused by spectral narrowing, and a sampling clock adjustment circuit that adjusts the sampling clock based on the detected phase shift information, thereby compensating for the degradation in detection sensitivity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system implements a feedback mechanism where the phase shift detection circuit continuously monitors phase shifts in the sampling clock, and this detection information is fed back to the sampling clock adjustment circuit. The adjustment circuit then modifies the sampling clock frequency or phase based on the feedback, creating a closed-loop system that automatically compensates for spectral narrowing effects and maintains optimal detection sensitivity

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If optical filters are used for wavelength processing, then wavelength demultiplexing and multiplexing can be performed, but jitter and wander tolerance of the optical signal is reduced

Engineering Contradiction:

Improvewavelength processing capabilityVSAvoidjitter and wander tolerance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The sampling clock synchronizing apparatus acts as an intermediary that isolates the impact of spectral narrowing. By detecting and compensating for phase shifts in the sampling clock, it prevents these phase shifts from directly affecting the optical signal's jitter and wander tolerance, thereby maintaining reliability despite the presence of optical filters

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The feedback loop in the sampling clock synchronizing apparatus continuously monitors and corrects phase shifts, creating a stabilizing effect that compensates for the jitter and wander introduced by optical filters. This closed-loop control maintains the optical signal's tolerance to timing variations despite the spectral narrowing caused by wavelength processing

Inventive Principle:

Principle #23Feedback

3Measurement precision

If spectral narrowing is compensated by using filter characteristics opposite to those of spectral narrowing, then detection sensitivity of sampling clock phase shift is improved, but device complexity increases

Engineering Contradiction:

Improvedetection sensitivity of sampling clock phase shiftVSAvoidcomplexity of sampling clock synchronizing apparatus

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system replaces complex hardware-based spectral narrowing compensation with a more sophisticated but electronically implementable approach: digital signal processing and control circuits. The phase shift detection and sampling clock adjustment are performed using electronic circuits and algorithms rather than additional physical filters, reducing mechanical and optical complexity while achieving the desired compensation effect

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of changing the physical characteristics of optical filters to compensate for spectral narrowing, the system changes the parameters of the sampling clock (frequency and phase) based on detected phase shifts. This parameter-based compensation approach achieves improved detection sensitivity through electronic adjustment rather than optical modification, thereby avoiding the complexity of designing and implementing inverse characteristic filters

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9014575B2Sampling clock synchronizing apparatus, digital coherent receiving apparatus, and sampling clock synchronizing method

Publication Date: 2015.04.21 1FINITY INC

AI summary

In a sampling clock synchronizing apparatus, an A/D converter converts an analog signal to a digital signal based on a sampling clock, and a processor compensates a band limitation due to spectral narrowing by filter characteristics of characteristics opposite to those of the spectral narrowing with respect to a signal produced from the A/D converter subjected to the spectral narrowing, and detects a phase shift in the sampling clock based on a signal after the compensation of the spectral narrowing and synchronizes sampling timing.