CFP2 Optical Transceiver with Erbium Doped Fiber Amplifier
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Solution Overview
Problem
Optical transceivers in coherent wavelength division multiplexing systems face challenges in achieving high-speed operation and reducing optical noise, particularly due to the large dimensions of dielectric MZ modulators and increased optical loss in semiconductor MZ modulators, which necessitate the use of fiber amplifiers to amplify signals while also dealing with amplified spontaneous emissions (ASE) that degrade signal quality.
Innovation Solution
The implementation of a wavelength tunable optical source and fiber amplifier with an ASE filter and variable optical attenuator, where the ASE filter has a tunable wavelength passing band to filter out ASE and the VOA adjusts output power to maintain preset levels, forming feedback loops to optimize the fiber amplifier's performance and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric MZ modulator is used to achieve sufficient optical interaction, then coupling efficiency is improved, but the device dimensions become too large for compact optical transceivers
Solution Approach 1:
The patent changes the material parameter (refractive index) by transitioning from dielectric material to semiconductor material, which enables the modulator to achieve sufficient optical interaction within a compact dimension while maintaining coupling efficiency
Solution Approach 2:
The patent introduces a new dimensional approach by integrating the modulator with a fiber amplifier system, allowing the compact modulator to compensate for its smaller size through external signal amplification, thus resolving the size-efficiency tradeoff
2Volume of moving object
If a semiconductor MZ modulator is used to reduce device dimensions, then compactness is improved, but optical loss increases
Solution Approach 1:
The patent introduces a fiber amplifier as an intermediary component that compensates for the optical loss generated by the semiconductor MZ modulator, allowing the system to maintain compact dimensions while recovering the energy loss through external amplification
Solution Approach 2:
The patent adds a new functional dimension by integrating a fiber amplifier into the system architecture, enabling the compact modulator to operate effectively despite its inherent optical loss through compensatory amplification
3Power
If a fiber amplifier is added to compensate for optical loss, then signal amplification is improved, but ASE noise degrades signal quality
Solution Approach 1:
The patent extracts and removes the harmful ASE noise component from the amplified signal using a dedicated filter, allowing the system to maintain signal amplification benefits while eliminating the degrading noise factor
Solution Approach 2:
The patent converts the harmful ASE noise into a detectable signal component by using a monitor photodiode to sense the ASE level, which then feeds back to control the pump power, transforming the noise from a detrimental factor into a control parameter for optimizing amplifier performance
4Object-generated harmful factors
If ASE filter and VOA are added to control noise and power, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback control mechanisms where monitor photodiodes sense the ASE noise level and output power, and the controller adjusts pump power and VOA settings accordingly, automating the noise reduction and power control functions to manage system complexity
Solution Approach 2:
The patent integrates multiple functions into existing components: the monitor photodiodes serve both to detect signal power and ASE noise, and the VOA serves both to control output power and to manage the impact of ASE noise, reducing the need for additional dedicated components
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 configuration allows for efficient power control and wavelength alignment, reducing ASE noise and maintaining target power levels, thereby enhancing signal quality and accuracy in high-speed optical communication systems.
Implementation Method 1
The fiber amplifier includes an erbium doped fiber (EDF), a pumping source, where the pumping source provides a pump beam to the EDF by which the EDF amplifies the light provided from the wavelength tunable optical source
Implementation Method 2
The ASE filter has a tunable wavelength passing band but filters out amplified spontaneous emissions out of the tunable wavelength passing band
Implementation Method 3
The VOA sets the output power of the fiber amplifier to a preset power by attenuating the amplified light received from the EDF
Implementation Method 4
The first mPD senses an output of the VOA, while, the second mPD senses an output of the ASE filter
Data Source
AI summary
An optical transceiver that includes an optical modulator of a Mach-Zehnder type and made of primarily semiconductor materials, and an Erbium Doped Fiber Amplifier (fiber amplifier) is disclosed. The fiber amplifier and the MZ modulator, in addition to a wavelength tunable laser diode, an intelligent coherent receiver, and a polarization maintaining splitter, are installed within a compact case following the standard of CFP2. The fiber amplifier provides a wavelength tunable filter that passes light amplified by the fiber amplifier but eliminates amplified spontaneous emission in regions out of the wavelength band of the light.