Optical Signal Pre-emphasis in Add-Drop Modules

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Optical amplifiers in transmission systems exhibit wavelength-dependent gain and noise figure, leading to performance differences between channels, and existing pre-emphasis methods fail to account for relative signal-to-noise ratio deteriorations across different channel categories in add-drop modules, resulting in suboptimal signal quality.

Innovation Solution

A method that calculates the optimum power distribution for all channels at add-drop modules, adjusting the average power of certain subbands to equalize signal-to-noise ratios, taking into account relative deteriorations and channel characteristics, and using data packets with counters and markings to control pre-emphasis steps across network sections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If separate pre-emphasis is performed for each subband with constant average channel power per subband, then the implementation is simple, but the red subband exhibits far worse performance than the blue subband due to wavelength-dependent noise figure

Engineering Contradiction:

Improvesimplicity of pre-emphasis implementationVSAvoidsignal-to-noise ratio performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the power distribution parameter across different subbands by redistributing total available power according to wavelength-dependent noise figures. Instead of maintaining constant average power per subband, the system adjusts power allocation to compensate for higher noise figures at certain wavelengths, thereby improving overall signal-to-noise ratio performance while maintaining implementation simplicity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If complete demultiplexing is undertaken at add-drop modules for individual channel power setting, then optimal signal quality can be achieved, but the cost increases significantly

Engineering Contradiction:

Improvesignal quality at end of transmission linkVSAvoidcost of add-drop module implementation

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the optical spectrum into subbands rather than requiring complete demultiplexing into individual channels. By operating at the subband level with broader spectral filters, the system achieves sufficient power control capability without the high cost and complexity of full channel-level demultiplexing, thereby reducing device complexity while maintaining acceptable signal quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The add-drop module is designed to handle multiple functions: it can drop specific channels while looping through entire subbands, and it can perform power control at the subband level. This multi-functionality allows the system to achieve optimal signal quality for dropped channels without requiring complete demultiplexing for all channels, thus reducing overall system complexity and cost.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If average channel power per subband is kept constant, then the pre-emphasis implementation is straightforward, but the red subband exhibits far worse performance than the blue subband

Engineering Contradiction:

Improveease of pre-emphasis configurationVSAvoidperformance equality between subbands

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7627248B2Method for pre-emphasis of optical signals in a transmission system comprising add-drop-modules

Publication Date: 2009.12.01 XIEON NETWORKS SARL

AI summary

A method for pre-emphasising transmitted signals in channels for multiplex signals along a transmission path comprising supply and/or branch points is provided. According to the method, relative degradations of the signal-to-noise intervals between transmitted signals via any category or group of channels—i.e. express and add or drop channels or add-drop channels are taken into account. A point-to-point link and for transparent optical networks may be used. To this end, the average signal powers of different channel groups are set relative to one another in order to obtain predetermined signal-to-noise intervals for each group. In addition, the signal-to-noise intervals within a channel group are equalized at their termination points. Regulation protocols for controlling the pre-emphasising steps are provided.