Laser Burst Control Circuit for 10G PON Systems
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Solution Overview
Problem
Conventional laser driver circuits for high-speed laser devices like DFB and EML lasers are limited to continuous-mode operation, failing to meet the burst-mode requirements of 10G PON systems, which necessitate external burst-mode control for efficient optical network unit (ONU) functionality.
Innovation Solution
A laser burst-mode control circuit that enables continuous-mode laser drivers to operate in burst-mode by using external switch circuits and bandwidth-select circuits, managed through high or low logic level inputs, allowing for fast-track and slow-track modes to ensure stable optical power and adaptability for DFB and EML lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional continuous-mode laser drivers are used for high-speed laser devices, then the laser devices can operate reliably, but they cannot operate in burst-mode which is required by 10G PON systems
Solution Approach 1:
The driver circuit is segmented into a continuous-mode laser driver and a separate burst-mode control circuit with external switches. The control circuit includes switch circuits that can be independently controlled to enable burst-mode operation without modifying the core continuous-mode driver, thus adding functionality while maintaining modular architecture.
Solution Approach 2:
The continuous-mode laser driver is designed to serve dual purposes: it can drive the laser in continuous-mode directly, or work in conjunction with the burst-mode control circuit to achieve burst-mode operation. This multi-functionality allows a single driver design to support both operation modes, eliminating the need for separate burst-mode specific drivers.
2Adaptability or versatility
If burst-mode control is added to enable 10G PON operation, then adaptability to PON systems is improved, but device complexity increases
Solution Approach 1:
A bandwidth-select circuit is introduced as an intermediary between the continuous-mode driver and the laser device. This circuit includes filter components (capacitors and resistors) that condition the drive signal to enable proper burst-mode operation. The intermediary circuit handles the complexity of burst-mode signal conditioning while keeping the main driver design simple and reusable.
Solution Approach 2:
The control circuit incorporates dynamically switchable bandwidth paths using switches and filter circuits. The bandwidth-select circuit can dynamically adjust its characteristics based on operational requirements, enabling fast-track mode for quick startup and slow-track mode for stable operation, thus adapting to different PON system states without permanent complex circuitry.
3Productivity
If external switch circuits are used for burst-mode control, then burst-mode operation is achieved, but the APC loop creation time may be affected
Solution Approach 1:
The burst-mode control circuit implements periodic switching of the laser device on and off according to PON system requirements. The control circuit is designed to manage these periodic operations efficiently, with the bandwidth-select circuit preparing the appropriate signal paths in advance to minimize setup time between bursts and ensure rapid APC loop re-establishment.
Solution Approach 2:
The bandwidth-select circuit is designed to pre-configure the appropriate filter paths (fast-track or slow-track) before burst operation begins. By having the switch circuits and filter circuits ready in advance and properly configured, the system minimizes the time required to establish the APC loop when burst-mode operation starts, thus reducing loop setup delay.
Data Source
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AI summary
A laser burst control circuit and method. The burst control circuit is added into an APC loop circuit, a switch is connected to a diode in series and then is connected to a laser in parallel, and by means of the on and off of an external logic control switch, a continuous-mode laser driver can work in a burst mode. Burst control also controls the switch and a bandwidth selection circuit by inputting a high and low logic level, wherein when a high level is input, the laser has no output, and meanwhile, the bandwidth selection circuit enters a quick tracking mode; when a low level is input, the laser outputs a normal optical signal; meanwhile, the bandwidth selection circuit enters a slow tracking mode, which makes sure that the APC loop circuit can work stably. The laser is controlled by an external switch circuit to respond rapidly, so that the requirement of a PON system on a burst mode index of an ONU can be met; meanwhile, the cost is low, and the realization is simple.