Wavelength Selective Switch Insertion Loss Correction
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Solution Overview
Problem
Wavelength selective switches in optical transmission systems exhibit wavelength-dependent insertion loss characteristics that vary with environmental temperature, making it challenging to maintain uniformity and desired profiles, especially in submarine cable systems, where aged deterioration further complicates accurate correction.
Innovation Solution
An optical transmission system that includes a wavelength selective switch, a light source, a multiplexer, light intensity monitors, a difference calculator, an insertion loss calculator, and a controller, which uses a dummy signal to estimate and correct insertion loss by calculating differences in light intensity across wavelengths, thereby adjusting the switch's insertion loss to compensate for temperature and aging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature resolution is increased to maintain uniform insertion loss accuracy at any environmental temperature, then the insertion loss uniformity is improved, but the storage apparatus size increases
Solution Approach 1:
The wavelength selective switch performs self-measurement of its insertion loss characteristics using an integrated light source and detector. The device autonomously acquires wavelength dependency data at multiple temperatures and stores it in its own memory, eliminating the need for external measurement equipment and large storage apparatuses. This self-service approach enables high-precision insertion loss correction while keeping the overall system compact.
2Measurement precision
If a temperature versus insertion loss wavelength dependency table is created before shipment, then the insertion loss can be corrected using pre-acquired data, but it is impossible to correct fluctuations due to aged deterioration
Solution Approach 1:
The system continuously monitors the actual insertion loss characteristics of the wavelength selective switch during operation and compares them with the stored reference data. When deviations are detected (such as those caused by aging), the system uses feedback control to adjust the insertion loss compensation values dynamically. This enables the device to adapt to long-term changes and maintain correction accuracy throughout its operational lifecycle.
Solution Approach 2:
The insertion loss correction is performed dynamically during operation rather than being fixed from pre-shipment measurements. The system can acquire new wavelength dependency data at different temperatures during service and update its correction tables in real-time. This dynamic approach allows the device to compensate for aging effects and environmental changes, maintaining high correction accuracy over time.
3Measurement precision
If additional insertion loss is adjusted for every single wavelength band to obtain flat insertion loss, then the insertion loss uniformity is improved, but the device complexity increases
Solution Approach 1:
The wavelength selective switch pre-acquires and stores its insertion loss wavelength dependency characteristics at multiple temperatures during manufacturing or initial calibration. These pre-measured data are stored in memory and used as reference for subsequent operation. During normal operation, the system retrieves the appropriate reference data based on current temperature conditions and applies compensation without requiring real-time complex measurements or adjustments for each wavelength band individually.
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 solution enables precise correction of wavelength-dependent insertion loss characteristics and temperature effects during operation, ensuring consistent signal intensity and OSNR across wavelengths, even in submarine cable systems, thereby improving the reliability and efficiency of optical transmission.
Implementation Method 1
a light source (12) that generates a dummy signal light
Implementation Method 2
a multiplexer (13) that multiplexes the main signal and the dummy signal light
Implementation Method 3
a wavelength selective switch (11) that switches the main signal
Implementation Method 4
light intensity monitors (14) that measure light intensity of the main signal and the dummy signal light
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A wavelength dependency of insertion loss characteristics of a wavelength selective switch is corrected during an operation of the wavelength selective switch. A multiplexer (13) inserts a dummy signal light generated by a light source (12) into a main signal and outputs the obtained signal to a wavelength selective switch (11). A light intensity monitor (14) acquires the intensity of the light of each wavelength of a light output from the wavelength selective switch (11). A light source controller (18) controls the insertion of the dummy signal light into the main signal, and release of the insertion. A difference calculator (15) calculates the difference between a first light intensity that the light intensity monitor (14) has acquired in a state in which the dummy signal light is inserted into the main signal and a second light intensity that the light intensity monitor (14) has acquired in a state in which the dummy signal light is not inserted into the main signal. An insertion loss calculator (16) calculates an insertion loss in the wavelength selective switch (11) based on the result of the calculation in the difference calculator (15). An insertion loss controller (17) controls the insertion loss in the wavelength selective switch (11) based on the calculated insertion loss.