Integrated Optical Interleaver Equalizer for ISI Suppression
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Solution Overview
Problem
As data rates increase in dense wavelength-division multiplexing (DWDM) communications, inter-symbol interference (ISI) caused by filtering effects in optical transmission paths becomes significant, existing solutions are either complex, costly, or not effectively achievable, especially at high speeds like 100 Gbps.
Innovation Solution
An integrated monolithic device combining an optical interleaver and equalizer with a raised-cosine filtering profile, using a Michelson interferometer configuration and fiber Bragg grating, suppresses ISI by compensating filtering effects from passive optical components, achieving channel density doubling and improved signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intra-channel optical equalization is implemented using separate optical components, then inter-symbol interference suppression is improved, but device complexity, cost, footprint, and optical loss increase
Solution Approach 1:
The patent combines the optical equalizer and optical interleaver into a single integrated device. The optical equalizer functionality is merged with the interleaver structure, eliminating the need for separate equalization components while maintaining ISI suppression capability. This integration directly reduces device complexity and component count.
Solution Approach 2:
The integrated device performs multiple functions simultaneously: it acts as both an optical equalizer for ISI suppression and an optical interleaver for channel combining/splitting. This multi-functionality reduces the overall number of components needed in the optical transmission system, lowering complexity and cost.
2Reliability
If intra-channel optical equalization is implemented using separate optical components, then inter-symbol interference suppression is improved, but cost and footprint increase
Solution Approach 1:
By merging the optical equalizer and interleaver into a single integrated device, the physical footprint is reduced. The combined structure eliminates the space required for separate equalization components and their associated mounting, alignment, and housing requirements.
3Reliability
If intra-channel optical equalization is implemented using separate optical components, then inter-symbol interference suppression is improved, but optical loss increases
Solution Approach 1:
The integration of equalization and interleaving functions into a single device reduces the number of optical interfaces, connections, and component interactions. This minimizes insertion loss, coupling loss, and alignment losses that would accumulate through multiple separate components, thereby reducing total optical loss.
4Productivity
If advanced modulation formats are used to improve spectral efficiency, then data rate is improved, but signal spectrum broadens increasing ISI
Solution Approach 1:
The optical equalizer performs preliminary equalization of the signal spectrum before detection. By pre-compensating for frequency-dependent attenuation and shaping the signal spectrum, the system can handle broader spectra from advanced modulation formats without suffering excessive ISI, enabling higher data rates.
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 reduces ISI, improving transmission performance with lower optical loss, smaller footprint, and lower costs, while being easily achievable and compatible with various modulation formats, enhancing signal quality and transmission capacity.
Implementation Method 1
the optical equalizer includes a passband that has a dip in the channel center to achieve a raised-cosine filtering profile in the optical signal path to achieve inter-symbol interference ISI suppression
Implementation Method 2
an interleaver configuration for combining or separating odd and even channel groups to achieve channel density doubling
Implementation Method 3
using a Michelson interferometer configuration and fiber Bragg grating, suppresses ISI by compensating filtering effects from passive optical components
Data Source
AI summary
An apparatus includes an interleaver configuration for at least one of combining or separating odd and even channel groups to achieve channel density doubling; and an optical equalizer for suppressing inter symbol interference within the channels to provide intra-channel equalizing in the optical path, the equalizer being integrated into the interleaver. Preferably, optical equalizer and interleaver are integrated together as a single monolithic device, the optical equalizer includes a passband that has a dip in the channel center to achieve a raised-cosine filtering profile in the optical signal path to achieve inter-symbol interference ISI suppression, and the equalizer includes integration into the optical path of the interleaver to realize a monolithic device combining or separating odd and even channel groups to achieve channel density doubling. Preferably, also, the optical equalizer includes a first equalizer with half the depth of required ripple dips at both a first output port and an input port and a second equalizer with half the depth of required ripple dips at a second output port.