Filtered Laser Array With AWG for WDM-PON
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Solution Overview
Problem
Wavelength division multiplexed (WDM) passive optical networks face inefficiencies in utilizing fiber bandwidth due to time domain multiplexing, which limits data rates and requires complex, costly tunable lasers for wavelength management, especially in applications needing a 'colorless' optical networking terminal (ONT) for ease of deployment and maintenance.
Innovation Solution
A filtered laser array assembly with external modulation, comprising an array of laser emitters coupled to an arrayed waveguide grating (AWG) for filtering and locking channel wavelengths, enabling high-speed modulation and wavelength selection without the need for continuous tuning or external wavelength locking mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If time domain multiplexing is used to share fiber among subscribers, then fiber deployment cost is reduced, but data rate and bandwidth utilization are limited
Solution Approach 1:
The patent transitions from time domain multiplexing to wavelength domain multiplexing by changing the fundamental parameter used for signal differentiation. Instead of assigning different time slots, the system assigns different wavelengths to different subscribers, enabling simultaneous transmission and dramatically increasing bandwidth utilization while maintaining cost-effective fiber deployment
Solution Approach 2:
The patent moves the multiplexing operation from the time dimension to the wavelength dimension. By utilizing the spectral dimension of optical signals, the system enables multiple subscribers to transmit data simultaneously on the same fiber without interference, thereby increasing productivity without sacrificing the cost benefits of fiber sharing
2Adaptability or versatility
If continuously tunable lasers are used to provide wavelength selection, then wavelength flexibility is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the continuously tunable laser into multiple discrete wavelength sources arranged in an array. Instead of using one complex continuously tunable laser, the system employs multiple simpler lasers each fixed at a specific wavelength, eliminating the need for continuous tuning mechanisms while maintaining wavelength selection capability
Solution Approach 2:
The patent introduces an arrayed waveguide grating (AWG) as an intermediary device to perform wavelength selection and filtering. The AWG receives light from multiple laser sources and routes or filters specific wavelengths to the output, enabling wavelength flexibility without requiring the lasers themselves to be continuously tunable
3Productivity
If external modulation is used to achieve high speed modulation, then data rate is improved, but device complexity increases
Solution Approach 1:
The patent combines the laser array, AWG filter, and external modulator into an integrated filtered laser array assembly. This merging of components simplifies the overall system architecture by pre-assembling the wavelength selection and modulation functions into a single modular unit, reducing the complexity burden despite the use of external modulation for high-speed data transmission
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 allows for efficient use of fiber bandwidth by enabling high-speed modulation and wavelength selection, reducing the complexity and cost of WDM-PON systems while allowing a single device to function across multiple subscriber locations with tunable wavelength capabilities.
Implementation Method 1
The arrayed waveguide grating (AWG) filters light from each of the laser emitters at different channel wavelengths
Implementation Method 2
The arrayed waveguide grating (AWG) filters light from each of the laser emitters at different channel wavelengths
Implementation Method 3
A back reflector is coupled to an output of the AWG and reflects the filtered light back to the laser emitters such that lasing cavities are formed
Implementation Method 4
Each of the laser emitters includes a gain region and an exit reflector. The AWG filters light from each of the laser emitters
Implementation Method 5
A plurality of external modulators are coupled to the laser emitters and are configured to modulate laser light exiting from respective ones of the laser emitters
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A filtered laser array assembly generally includes an array of laser emitters coupled between external modulators and an arrayed waveguide grating (AWG). Each of the laser emitters emits light across a plurality of wavelengths including, for example, channel wavelengths in an optical communication system. The AWG filters the emitted light from each of the laser emitters at different channel wavelengths associated with each of the laser emitters. Lasing cavities are formed between each of the laser emitters and a back reflector coupled to an output of the AWG such that laser output from the laser emitters is provided at the respective channel wavelengths of the reflected, filtered light. The external modulators enable high speed modulation of the laser output. The modulated laser output may then be optically multiplexed to produce an aggregate optical signal including multiple channel wavelengths.