Wavelength Blocking Filter for ASE Noise Suppression in Optical Add/Drop Devices

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Colorless optical add/drop devices face challenges with higher order modulation formats due to accumulated Amplified Stimulated Emission (ASE) noise and high insertion loss, which exceed Received Optical Signal-to-Noise Ratio (ROSNR) requirements, especially at rates of 200 Gb/s and above, leading to unworkable noise penalties.

Innovation Solution

Implementing a noise suppression system prior to the colorless optical add/drop device using a wavelength blocking filter array and single channel amplifier array, which includes flexible bandwidth filters like Liquid Crystal on Silicon (LCOS) and Digital Light Processing (DLP) filters, to suppress out-of-band ASE noise and provide amplification, thereby improving OSNR and supporting higher order modulation formats.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If colorless multiplexer structures rely on power combining of multiple signals, then flexibility in add/drop requirements is improved, but accumulated ASE noise increases significantly

Engineering Contradiction:

Improveflexibility in add/drop requirementsVSAvoidaccumulated ASE noise

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by filtering out-of-band ASE noise from individual optical signals before they enter the power combiner. Wavelength blocking filters are positioned upstream of the combiner to pre-cleanup each signal, preventing noise accumulation at the combination point while maintaining the flexible colorless multiplexer architecture

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If colorless multiplexer structures use power combining without prior amplification, then device complexity is reduced, but insertion loss increases and noise penalty becomes unworkable

Engineering Contradiction:

Improvemultiplexer structure simplicityVSAvoidinsertion loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent implements preliminary amplification using single-channel amplifiers positioned before the power combiner. Each signal is amplified individually prior to combination, ensuring sufficient power levels are achieved before mixing. This preliminary gain stage reduces the impact of subsequent insertion losses while maintaining relative structural simplicity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the amplification function into individual single-channel amplifiers for each wavelength path, rather than using a single bulk amplifier. This segmentation allows precise control of gain per channel and enables the system to handle high-order modulation formats by ensuring each signal maintains adequate power levels through the combiner

Inventive Principle:

Principle #1Segmentation

3Productivity

If higher order modulation formats are used to increase capacity, then data rate is improved, but ROSNR requirements become significantly higher

Engineering Contradiction:

Improvedata rateVSAvoidROSNR requirement

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary noise filtering using wavelength blocking filters that remove out-of-band ASE noise before signals undergo high-order modulation or pass through the combiner. This pre-cleaning of noise ensures that signals entering the high-capacity modulation stage have optimal signal-to-noise characteristics, enabling 200 Gb/s and above rates to meet their stringent ROSNR requirements

Inventive Principle:

Principle #10Preliminary action

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

The solution effectively suppresses ASE noise and amplifies signals, enabling the use of higher order modulation formats at 200 Gb/s and above by improving ROSNR, reducing insertion loss, and allowing for a mixed population of modems in the same colorless multiplexer structure, thus simplifying operations and reducing costs.

Implementation Method 1

filtering the optical signal with a wavelength blocking filter to suppress out of band Amplified Stimulated Emission (ASE) in order to prevent noise funneling

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Implementation Method 2

amplifying the optical signal with a single channel amplifier; suppress out of band Amplified Stimulated Emission (ASE)

Methodology Applied

Scientific EffectAmplified Stimulated Emission:

Data Source

PatentUS10277352B2Noise suppression and amplification systems and methods for colorless optical add/drop devices

Publication Date: 2019.04.30 CIENA CORP

AI summary

A method for noise suppression in a colorless optical add/drop system implemented prior to a colorless optical add/drop device includes, subsequent to receiving an optical signal from an optical modem, filtering the optical signal with a wavelength blocking filter to suppress out of band Amplified Stimulated Emission (ASE) in order to prevent noise funneling in the colorless optical add/drop device; and providing the filtered optical signal with the out of band ASE suppressed therein to a multiplexer port in the colorless optical add/drop device. The method can include, prior to the filtering, amplifying the optical signal with a single channel amplifier, wherein the single channel amplifier can include a pump laser shared with one or more additional single channel amplifiers.