Optical Line Controller Wavelength Tuning for OBI Reduction
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Solution Overview
Problem
Passive optical networks (PONs) face performance degradation due to optical beat interference (OBI) caused by imperfect isolation in optical circulators, leading to noise and reduced efficiency in bidirectional signal transmission.
Innovation Solution
A controller circuitry for optical line terminals (OLTs) in PONs adjusts the wavelength of downstream signals based on the level of OBI derived from existing signals, ensuring they differ from upstream signals to reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical circulators are used to provide isolation between transmitting and receiving paths, then bidirectionality is supported, but optical beat interference increases due to imperfect isolation
Solution Approach 1:
The patent dynamically adjusts the wavelength of the downstream optical signal based on the measured level of optical beat interference. By changing the wavelength parameter, the system forces the downstream wavelength to differ from the upstream wavelength, thereby reducing OBI while maintaining bidirectional operation through the optical circulator
2Productivity
If higher optical bitrate is used, then network capacity increases, but component cost increases
Solution Approach 1:
The system uses the existing upstream signal itself to measure the level of optical beat interference and automatically adjusts the downstream wavelength based on this measurement. This self-service approach eliminates the need for additional external control signals or complex calibration equipment, reducing component costs while enabling high bitrate operation
3Productivity
If in-band full-duplex mode is used, then bandwidth per wavelength is doubled, but optical beat interference from simultaneous transmission increases
Solution Approach 1:
The patent implements a feedback mechanism where the downstream wavelength is continuously adjusted based on the measured level of optical beat interference from the upstream signal. This feedback loop allows the system to maintain in-band full-duplex operation with doubled bandwidth while dynamically compensating for OBI by forcing wavelength separation
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
This approach enhances PON performance by reducing OBI without the need for additional components, doubling bandwidth per wavelength, and operating within existing component tolerances, thus maintaining efficiency and reducing costs.
Implementation Method 1
an optical receiver and configured to receive the upstream optical signal
Implementation Method 2
amplifying the monitored signal thereby obtaining an amplified signal
Implementation Method 3
high-pass filtering the amplified signal thereby obtaining a filtered signal
Data Source
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AI summary
Example embodiments describe a controller circuitry (610, 740) for controlling an optical transceiver of an optical line terminal (100), OLT, in a passive optical network (150), PON, comprising means for performing deriving (901) a level of optical beat interference, OBI, of a received upstream optical signal (102) from an optical transceiver of an optical network terminal (101), ONT; and setting (902) a wavelength (120) of a downstream optical signal (103) based on the level of OBI such that the wavelength (120) is forced to differ from the upstream optical signal wavelength (121).