FP-LD Transmitter With Fiber Bragg Grating Feedback
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Solution Overview
Problem
Current optical access networks face limitations with FP-LD transmitters due to multimode characteristics, which restrict modulation rate and transmission distance, and tunable lasers are costly, hindering the deployment of high-bandwidth NG-PON2 systems like TWDM-PON.
Innovation Solution
Integration of a fiber Bragg grating (FBG) or tunable FBG with FP-LD to form a feedback cavity, allowing for self-injection locking and wavelength tuning, reducing the need for external optical sources and expensive tunable lasers, while maintaining performance comparable to DFB-LD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If external injection locking mode is used to improve FP-LD transmission characteristic, then modulation bandwidth and transmission distance are improved, but system cost increases due to additional light source at each ONU
Solution Approach 1:
The patent combines the external light source with the FP-LD to form an integrated transmitter module, merging two previously separate components (external laser source and FP-LD) into a single unit. This integration eliminates the need for separate light sources at each ONU while maintaining the benefits of external injection locking, thereby improving modulation bandwidth without increasing system cost.
Solution Approach 2:
The integrated transmitter module serves multiple functions: it provides both the external injection light and the FP-LD operation, acts as a wavelength selector, and functions as the complete transmission source. This multi-functionality replaces what previously required separate components, reducing system complexity and cost while maintaining improved transmission characteristics.
2Stability of the object's composition
If external injection locking mode is used, then single-mode output with constant power is achieved, but device integration into ONU module unit becomes difficult
Solution Approach 1:
The patent merges the external light source and FP-LD into a single integrated transmitter module that can be easily incorporated into ONU equipment. This integration maintains the stable single-mode output characteristic while solving the manufacturing and deployment complexity issue by providing a compact, pre-integrated unit.
3Reliability
If external seed light source is used, then mode partition noise is reduced, but the active component requires on/off control mechanism
Solution Approach 1:
By integrating the external light source and FP-LD into a single module, the patent eliminates the need for separate control mechanisms for the external source. The integrated design allows the FP-LD to be directly modulated while maintaining the noise-reduction benefits, simplifying the control architecture.
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 significantly reduces system costs by enabling high modulation rates and longer transmission distances with FP-LD, while being easy to integrate and implement, saving up to 6400$ per 40G TWDM-PON system with 64 ONUs.
Implementation Method 1
the fiber Bragg grating is for filtering the received multiple-longitudinal mode light wave according to a predetermined parameter
Implementation Method 2
the optical coupler is for dividing the optical signal to a first branch optical signal and a second branch optical signal
Data Source
Figure 1~2
Figure 3~4(a)
Figure 4(b)~4(c)
AI summary
The invention proposes an optical transmitter, comprising: a FP-LD, generating multiple-longitudinal mode light wave, wherein the FP-LD is also driven by an electrical signal, modulating the electrical signal to the multiple-longitudinal mode light wave, and outputting the modulated multiple-longitudinal mode light wave; an optical coupler, coupled with the FP-LD, wherein the coupler is used for feeding the modulated multiple-longitudinal mode light wave from the FP-LD to a fiber Bragg grating; the fiber Bragg grating is for filtering the received multiple-longitudinal mode light wave according to a predetermined parameter, and feeding back the optical signal generated after being filtered to the optical coupler; the optical coupler divides the optical signal, thus making the optical signal oscillate between the FP-LD and the fiber Bragg grating to form a oscillation cavity, and outputs a single mode optical wave with constant wavelength and power.