Coherent WDM Node With Bandpass Add-Drop Filtering
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Solution Overview
Problem
Existing network nodes for coherent optical WDM transmission networks require high attenuation and costly optical amplification due to the use of full-spectrum filters or 1×N power splitters, leading to increased circuitry and costs, and lack effective noise shaping.
Innovation Solution
A network node design utilizing a passive optical filter device that segments the optical spectrum into bands assigned to different local ports, combined with an optical router, allowing for flexible channel addition and dropping with reduced insertion loss and enabling flexgrid capability, using low-cost white-band filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a full-spectrum filter is used to define local ports for each optical channel, then each optical channel can be added and dropped at dedicated ports, but the insertion loss increases requiring optical amplification
Solution Approach 1:
The optical spectrum is segmented into multiple bands (e.g., first optical band, second optical band, etc.) rather than treating each channel individually. Each band is assigned to a different local port, allowing multiple channels to share the same port. This segmentation reduces the number of ports needed while maintaining channel management capability, thereby reducing insertion loss without requiring optical amplification.
2Adaptability or versatility
If a full-spectrum filter defines a high number of local ports for each optical channel, then channel management flexibility is improved, but the device complexity and costs increase
Solution Approach 1:
Each local port is designed to handle multiple optical channels simultaneously by assigning multiple channels to the same port. This multi-functionality allows a single port to serve multiple purposes, reducing the total number of ports required while maintaining the ability to manage all channels. The solution achieves channel management flexibility without proportionally increasing device complexity.
3Adaptability or versatility
If a 1×N power splitter is used to define local ports, then the number of ports is increased, but the insertion loss increases and no out-of-band noise shaping is obtained
Solution Approach 1:
The patent employs passive optical filters with relatively simple structures (analogous to disposable, low-cost components) that achieve effective noise shaping and channel separation without requiring complex or expensive components. These filters provide sufficient performance for channel management while avoiding the high insertion loss and complexity of power splitters, achieving both port capability and noise shaping with low-cost components.
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 reduces circuitry and costs while achieving sufficient noise shaping and avoiding optical amplification, allowing for flexible redefinition of the WDM grid and efficient channel management with low-cost components.
Implementation Method 1
a passive optical filter device which segments the whole optical spectrum, i.e. the full optical spectrum covering all optical channels of the WDM transmission network, into a given number of optical bands
Data Source
AI summary
Provided is a network node for a coherent optical wavelength division multiplex (WDM) transmission network including at least one remote port which is adapted to receive from and/or output to neighboring network nodes an optical WDM signal including one or more optical channel signals each lying within an optical channel of an optical WDM transmission band and a predetermined number N of local ports, each local port being adapted to receive from a dedicated coherent optical transmitter an optical add channel signal which is to be integrated in an optical WDM signal that is output at a remote port and/or each local port being adapted to output to a respective dedicated optical receiver an optical drop channel signal. The network node includes an optical router device that defines the at least one remote port and further defines an internal remote port, the optical router device being configured to route one or more selected or all optical channel signals included in the optical WDM signal received at a selected remote port as optical drop channel signals to the internal remote port and/or to route one or more optical add channel signals received at the internal remote port to one or more selected remote ports or to all remote ports. The network node further includes a passive optical filter device which is connected, at an internal remote port of the passive optical filter device, to the internal remote port of the optical router device, and which further defines the predetermined number N of local ports. The passive optical filter device is configured to define N optical bandpass filter functions each of which describes a bandpass filter characteristic between the internal remote port of the passive optical filter device and a selected, respectively differing local port. The passband of each optical bandpass filter function covers two or more neighboring optical channels. The passbands of all optical bandpass filter functions differ from each other with respect to the optical channels covered.