Adaptive Gain Control for MEMS WSS OSNR Penalty
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The introduction of reconfigurable optical add-drop multiplexers (ROADMs) with micro-electromechanical system (MEMS)-based wavelength selective switches (WSSs) leads to increased noise due to side-lobes, causing an optical signal-to-noise ratio (OSNR) penalty, as current ASE compensation methods underestimate accumulated ASE power, resulting in signal power drops and network performance impairment.
Innovation Solution
Adaptive gain control systems that measure and adjust amplifier target power based on side-lobe size and OSNR, using formulas like Side_Lobe_Penalty=0.0045x^2−0.115x to calculate ASE power in side-lobes, allowing for precise adjustment of variable optical attenuators to maintain signal launching power and compensate for OSNR penalties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MEMS-based WSS ROADMs are introduced to enable dynamic wavelength switching, then network reconfigurability and flexibility are improved, but ASE noise accumulates in side-lobes causing OSNR penalty
Solution Approach 1:
The system performs preliminary estimation of ASE power in side-lobes using a derived formula based on WSS attenuation settings before signals propagate through the network. This allows the network controller to pre-calculate the cumulative ASE penalty and adjust amplifier target powers in advance to compensate for the expected noise accumulation, preventing OSNR degradation before it occurs.
Solution Approach 2:
The system implements a feedback mechanism where the network controller continuously monitors WSS attenuation settings and recalculates ASE power estimates. Based on this feedback, the controller dynamically adjusts amplifier target powers to maintain adequate OSNR margins, enabling the system to adapt to changing network configurations and compensate for accumulated side-lobe noise.
2Strength
If amplifier target power is increased to compensate for ASE noise, then signal power is improved, but system complexity increases due to adaptive control requirements
Solution Approach 1:
The network controller serves as an intermediary that centralizes the complex calculations and decision-making for ASE compensation. Instead of requiring complex adaptive control logic in each amplifier and WSS device, the controller performs the sophisticated ASE power estimation using the derived formula and coordinates power adjustments across the network, simplifying the overall system architecture while maintaining effective compensation.
3Ease of operation
If traditional ASE compensation methods are used, then implementation is simple, but ASE power is underestimated leading to signal power drops
Solution Approach 1:
The system introduces a derived formula that incorporates WSS attenuation parameters to calculate ASE power in side-lobes. By changing the estimation approach from assuming uniform ASE distribution to using a parameter-based calculation that accounts for actual WSS settings, the system achieves more precise ASE power estimation while maintaining relatively simple implementation through centralized control.
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 adaptive gain control effectively estimates and compensates for ASE power in side-lobes, preventing OSNR penalties and maintaining signal quality across networks with WSS-based ROADMs, thereby enhancing network performance.
Implementation Method 1
An input fiber including multiple wavelengths λ1, λ2, . . . λn of optical signals is input into a de-multiplexer 11, such as a diffraction grating. The de-multiplexer 11 separates each wavelength from the common input
Implementation Method 2
The WSS 10 includes a MEMS mirror 12 for each of the wavelengths λ1, λ2, . . . λn. The MEMS mirror 12 is a micro-mirror that deflects the optical signal to an appropriate output port 13
Implementation Method 3
optionally a variable optical attenuator (VOA) 14 can be included following the de-multiplexer 11. VOAs 14 are configured to provide variable attenuation to the wavelength
Implementation Method 4
Amplified spontaneous emission (ASE) noise is one of the main noise sources in optical amplifiers. ASE is initiated by spontaneous decay of electrons, creating photons
Data Source
AI summary
The present invention provides systems and methods to adaptively control amplifier target power to maintain signal launching power as per design in networks with wavelength selective switch (WSS)-based reconfigurable optical add-drop multiplexers (ROADMs) using micro-electromechanical system (MEMS). Accordingly, signal OSNR does not collapse faster for WSS-based ROADMs than other similar configured system without WSS-based ROADM. In order to correct amplifier target power, the present invention utilizes system information about side-lobe size and OSNR at each amplifier. Related information, such as ASE level and size of side-lobes at each channel from upstream amplifiers, is passed to the network controller at each amplifier. Meanwhile, with target signal level and local WSS attenuation setting (given side-lobe size vs. WSS attenuation known) of each channel, the amplifier calculates what is total output power should be and adaptively maintains that power.