Athermal External Cavity Laser Using Negative Thermooptical Polymer
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Solution Overview
Problem
Wavelength division multiplexing (WDM) passive optical networks face challenges with mode hopping in external cavity lasers (ECLs) due to temperature variations, leading to unstable oscillation wavelengths and rapid changes in optical power, which deteriorate transmission quality and device reliability.
Innovation Solution
An athermal external cavity laser design is implemented, utilizing a semiconductor amplifier, optical fiber with a Bragg grating, and a thermosetting polymer with a negative thermooptical coefficient, along with an optical path compensator, to maintain stable output optical power and wavelength regardless of temperature changes without additional temperature control components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional ECL with Bragg grating is used, then manufacturing cost is reduced compared to DFB-LD, but mode hopping occurs due to temperature variations causing unstable oscillation wavelength and rapid optical power changes
Solution Approach 1:
The patent changes the physical parameters of the ECL system by introducing a specific cavity length range (0.5mm to 2mm) and using athermally compensated mounting structures to alter how the system responds to temperature variations, thereby preventing mode hopping while maintaining cost-effectiveness
Solution Approach 2:
The patent addresses thermal effects by designing the mounting structure to compensate for thermal expansion and contraction of components. The athermal mounting technique balances the thermal expansion coefficients of different materials to maintain stable optical alignment and cavity length across temperature variations
2Reliability
If temperature control components (TEC, thermistor) are added to DFB-LD, then oscillation wavelength stability is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent extracts and removes the expensive temperature control components (TEC, thermistor, temperature control circuit) from the system, replacing them with a passive athermal mounting structure that achieves wavelength stability without active temperature control, thereby significantly reducing manufacturing cost
Solution Approach 2:
The patent implements a self-regulating system where the athermal mounting structure passively compensates for temperature variations through its mechanical design, eliminating the need for external temperature control components and their associated control circuits
3Reliability
If monitoring photodetector and wavelength fixing unit are added to ECL, then oscillation stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the monitoring photodetector and wavelength fixing unit from the system, demonstrating that proper athermal mounting design alone is sufficient to maintain oscillation stability without these additional components, thereby reducing manufacturing cost
4Reliability
If athermal mounting structure is implemented, then mode hopping is eliminated and wavelength stability is improved, but device complexity increases
Solution Approach 1:
The patent applies athermal mounting techniques specifically to the critical regions where temperature sensitivity causes mode hopping, rather than implementing complex athermal designs throughout the entire device. This targeted approach achieves wavelength stability with minimal increase in overall device complexity
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 athermal ECL ensures regular output optical power and wavelength stability, reducing manufacturing costs and improving the reliability of WDM PON systems by eliminating mode hopping and the need for expensive temperature control modules.
Implementation Method 1
an optical fiber 30 of a core 32 in which a Bragg grating 34 is formed and a cladding 36 surrounding the core 32. The Bragg grating 34 of the optical fiber 30 is stable against temperature variations
Implementation Method 2
a thermosetting polymer that fixes the optical fiber to a ferrule and has a negative thermooptical coefficient
Data Source
AI summary
Provided is an athermal external cavity laser (ECL), whose output optical power and output wavelength can be kept regular irrespective of temperature changes without using additional temperature controlling components. The ECL comprises: a semiconductor amplifier; an optical fiber comprising a core in which a Bragg grating is formed and a cladding surrounding the core; and a thermosetting polymer that fixes the optical fiber to a ferrule and has a negative thermooptical coefficient, wherein the thickness of the cladding surrounding the core in which the Bragg grating is formed is smaller than the portion of the cladding surrounding the portion of the core where the Bragg grating is not formed, and the thermosetting polymer the negative thermooptical coefficient surrounds the cladding. The ECL does not need additional temperature controlling components and thus can be manufactured compact and at low cost, and thus can be used as a light source of a dense wavelength division multiplexing (DWDM) system in designing economical WDM passive optical networks (PON).