Pilot Tone Wavelength Locking in Optical Transmission
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Solution Overview
Problem
Conventional optical transmission systems face bandwidth limitations due to the need for additional communication channels, which diminish the available data bandwidth for wavelength division multiplexing channels.
Innovation Solution
A method that generates a pilot tone with an adjustable frequency to identify wavelength division multiplexing channels, modulates this tone with data to create a pilot tone data signal, and transports it alongside a high-frequency data signal to a remote central wavelength locker for demodulation, allowing for remote wavelength locking and embedded communication without reducing bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional communication channels are used for control data transmission, then control functionality is improved, but available data bandwidth is reduced
Solution Approach 1:
The patent combines control data transmission and wavelength monitoring functions with the existing WDM data channels by using pilot tones. Instead of adding separate communication channels, the system embeds control information in pilot tones that are multiplexed alongside data signals, allowing control functionality to be achieved without reducing available data bandwidth.
Solution Approach 2:
The pilot tones serve multiple functions simultaneously: they enable wavelength monitoring, provide channel identification, carry control data, and assist in amplifier gain control. This multi-functionality eliminates the need for dedicated separate channels for these control purposes, thereby preserving data bandwidth while improving control reliability.
2Measurement precision
If pilot tones are used for wavelength monitoring, then monitoring capability is improved, but system complexity increases
Solution Approach 1:
The system uses the existing WDM infrastructure and pilot tones already present in the optical signal to perform wavelength monitoring and control functions. The pilot tones self-identify their wavelength through frequency detection, and the system leverages existing amplifier gain control mechanisms, eliminating the need for additional expensive equipment like tunable optical filters or diffraction gratings.
Solution Approach 2:
The patent replaces complex mechanical/optical filtering systems (tunable filters, diffraction gratings) with electronic signal processing methods. By detecting pilot tone frequencies electronically and using them for wavelength identification and control, the system achieves precise wavelength monitoring without the complexity and cost of mechanical optical filtering components.
3Stability of the object's composition
If remote wavelength locking is implemented, then wavelength stability is improved, but system complexity increases
Solution Approach 1:
The system implements remote wavelength locking by using pilot tones as feedback signals. The pilot tone frequency detected at the receiving end provides real-time information about wavelength drift, which is used to adjust the laser source wavelength to maintain stability. This feedback mechanism achieves wavelength locking without requiring complex local wavelength stabilization equipment at remote locations.
Solution Approach 2:
The pilot tones act as intermediaries between the laser source and the wavelength monitoring system. Instead of directly monitoring the high-frequency optical laser signal which would require complex equipment, the system uses the lower-frequency pilot tones that modulate the optical signal as mediators to carry wavelength information, simplifying the wavelength locking implementation.
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
Enables efficient remote wavelength locking and embedded communication within optical transmission systems, increasing data transmission bandwidth and making control data independent of the application data stream without additional circuitry or complexity.
Implementation Method 1
converting the received optical laser signal by means of a photo diode of said remote central wavelength locker to provide a pilot tone data signal
Data Source
AI summary
A method for operating an optical transmission system (1), the method comprising the steps of: (a) generating (S1) for a tunable laser (L) a pilot tone (PT) having an adjustable pilot tone frequency (fPT) which identifies a wavelength division multiplexing (WDM) channel used by the respective tunable laser (L); (b) multiplying (S2) the generated pilot tone (PT) of said tunable laser (L) with pilot tone data (PTD) to provide a pilot tone data signal (PTDS); (c) supplying (S3) the pilot tone data signal (PTDS) and a high frequency data signal (HFDS) to said tunable laser (L) which generates an optical laser signal (OLS) output by said tunable laser (L) in response to the supplied signals; (d) transporting (S4) said optical laser signal (OLS) to a remote central wavelength locker (3G) via an optical transport medium (5); (e) converting (S5) the received optical laser signal (OLS) by means of a photo diode (PD) of said remote central wavelength locker (3G) to provide a pilot tone data signal (PTDS) for wavelength division multiplexing (WDM) channels which is demodulated to detect the pilot tone (PT) and the pilot tone data (PTD) for each individual wavelength division multiplexing (WDM) channel; and (f) identifying (S6) the wavelength division multiplexing (WDM) channel used by the respective tunable laser (L) on the basis of the pilot tone frequency (fPT) of the detected pilot tone (PT) and evaluating the pilot tone data (PTD) of the identified wavelength division multiplexing (WDM) channel.