Wavelength Selective Switch Crosstalk Reduction

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Solution Overview

Problem

Coherent crosstalk in colorless, directionless, and contentionless optical networks due to imperfect isolation of reconfigurable filters in wavelength selective switches, leading to signal degradation and noise interference.

Innovation Solution

Implementing wavelength channel plans where only non-adjacent carriers are supplied to the input ports of wavelength selective switches to minimize the impact of coherent crosstalk, by configuring the channel plan to prevent adjacent wavelength interactions and using guard-bands to accommodate filtering effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If reconfigurable filters are used to block unwanted wavelengths in wavelength selective switches, then wavelength routing capability is improved, but coherent crosstalk increases due to imperfect isolation

Engineering Contradiction:

Improvewavelength routing capabilityVSAvoidcoherent crosstalk

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the wavelength assignment parameters by introducing guard-bands between adjacent wavelength channels. This parameter modification ensures that blocked wavelengths are sufficiently separated from passed wavelengths, preventing coherent crosstalk while maintaining the adaptability of wavelength routing in reconfigurable optical add-drop multiplexers.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces guard-bands as intermediary spectral regions between adjacent wavelength channels. These guard-bands act as buffers that prevent direct interaction between blocked and passed wavelengths, thereby reducing coherent crosstalk without compromising the wavelength routing functionality of the reconfigurable filters.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If adjacent wavelength channels are used to maximize spectral efficiency, then bandwidth utilization is improved, but coherent crosstalk increases due to filter leakage

Engineering Contradiction:

Improvebandwidth utilizationVSAvoidcoherent crosstalk from aggressor wavelengths

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the wavelength channel assignment parameters by introducing guard-bands between adjacent channels. This allows the system to maintain high bandwidth utilization with adjacent wavelength channels while the guard-bands prevent coherent crosstalk by ensuring sufficient spectral separation between blocked and passed wavelengths.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If reconfigurable filters block M wavelengths to achieve desired routing, then wavelength selectivity is improved, but signal-to-noise ratio deteriorates due to filter imperfections

Engineering Contradiction:

Improvewavelength selectivityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the spectral parameter arrangement by introducing guard-bands between wavelength channels. This allows reconfigurable filters to achieve high wavelength selectivity for blocking M wavelengths while the guard-bands prevent filter imperfections from causing coherent crosstalk, thereby maintaining a high signal-to-noise ratio.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly reduces coherent crosstalk, enhancing the signal-to-noise ratio and improving the overall performance of optical communication systems by preventing 'aggressor' wavelength leakage and optimizing filter responses.

Implementation Method 1

The wavelength selective switch has a plurality of input ports, and functions to combine and shape the spectrum of light received at the input ports into a single combined signal that is passed onto the fiber optic cable. Shaping the light received at the plurality of input ports includes blocking optical signals having undesired wavelengths of light received at the input ports

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Implementation Method 2

each of the input ports of the wavelength selective switch includes a separate reconfigurable filter. The reconfigurable filters in the wavelength selective switch are constituted by a combination of individually controllable 'slices' of spectrum. The wavelength selective switch sets the attenuation of each individual slice of spectrum to achieve the filter shape required to either block or allow through a wavelength

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Implementation Method 3

ROADMs may also be provided with a splitter which splits light and directs the light to ports of the wavelength selective switches. In colorless, directionless and contentionless networks, the splitter broadcasts each wavelength of light to all of the N degrees of the node

Methodology Applied

Scientific EffectOptical splitting:

Data Source

PatentUS11251894B2Apparatus and method to reduce the impact of coherent crosstalk in optical networks

Publication Date: 2022.02.15 INFINERA CORP

AI summary

Optical networks, nodes and methods are disclosed. To solve the aggressor issue and to reduce the cross-talk caused by the aggressors in colorless, directionless and contentionless reconfigurable optical add drop multiplexer nodes, the present disclosure configures a first broadcast module to supply only non-adjacent wavelengths to a first input port of a wavelength selective switch, and a second broadcast module to supply only non-adjacent wavelengths to a second input port of the wavelength selective switch.