Laser Device Extinction Ratio via Envelope Signal Switching
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Solution Overview
Problem
Optical modulators in existing laser devices for burst mode systems suffer from low extinction ratios, leading to residual light emission even when driven by a shut-off signal, causing misinterpretation of logical values in dense wavelength division multiplex systems where multiple devices transmit simultaneously.
Innovation Solution
A laser device with a filter generating an envelope signal to switch the laser driver on and off, ensuring no residual light is emitted when not transmitting, and a dual power consuming laser light source to stabilize wavelength variations due to thermal fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical modulator means are used to modulate the laser light beam, then data transmission is enabled, but residual light is emitted even when shut-off signal is applied causing low extinction ratio
Solution Approach 1:
The system separates the laser light generation and modulation functions into distinct components: a laser driver controls the laser light source while an optical modulator independently modulates the beam. This segmentation allows the laser driver to be switched off completely (achieving full extinction) while the modulator handles only the modulation function, resolving the contradiction between enabling data transmission and eliminating residual light.
Solution Approach 2:
The laser driver is switched off in advance during periods when no data packets are being transmitted. By preliminarily stopping the laser light generation before any potential residual emission could occur, the system achieves complete extinction ratio while still enabling rapid modulation when data transmission is required.
2Productivity
If multiple laser devices operate simultaneously on the same wavelength in DWDM systems, then channel capacity is increased, but residual lights from multiple devices sum up causing misinterpretation of logical values
Solution Approach 1:
The laser driver operates in periodic bursts synchronized with data packet transmission. During idle periods between packets, the laser driver is completely switched off, eliminating residual light accumulation. This periodic on-off operation allows multiple devices to share the same wavelength channel without their residual lights summing up to cause detection errors, thereby maintaining both high channel capacity and reliable data detection.
3Productivity
If laser driver is switched on and off rapidly for packet transmission, then burst mode operation is achieved, but thermal fluctuations cause wavelength variations
Solution Approach 1:
A preliminary current is supplied to the laser light source before actual data transmission begins. This preliminary action pre-heats the laser diode, stabilizing its temperature and wavelength characteristics before burst mode operation commences. By performing this thermal preparation in advance, the system achieves rapid burst mode transmission while minimizing wavelength variations caused by thermal fluctuations during the actual data packets.
Data Source
AI summary
A Laser device for optical packet data transmission in TDM-systems is provided. The device comprises a laser light source for outputting laser light beam and a laser driver for driving the laser light source; an optical modulator which receives and modulates the laser light beam output by the laser light source; a packet data source for outputting a packet data stream; and a modulator driver for receiving the packet data stream output by the packet data source and for driving the optical modulator in response to the packet data stream resulting in that the optical modulator modulates the laser light beam in response to the packet data stream. A filter generates an envelope signal of the data packets in the packet data stream, and a switch switches the laser driver in response to the envelope signal.