TEC (Thermo Electric Cooler) starting circuit of electro-absorption modulated laser

Abstract

The invention provides a TEC (Thermo Electric Cooler) starting circuit of an electro-absorption modulated laser. The TEC starting circuit comprises a power circuit, a TEC control circuit, a laser integrating a TEC and a thermistor NTC (Negative Temperature Coefficient), a TEC closed loop feedback circuit, a current buffer circuit, a P-MOS (P-Metal Oxide Semiconductor) transistor, a first capacitor, a second capacitor and a fifth resistor, wherein the current buffer circuit is positioned between an output end of the power circuit and a power input end of the TEC control circuit; a source electrode S of the P-MOS transistor is connected with the output end of the power circuit and one end of the first capacitor, and the other end of the capacitor is connected with a gate electrode G of the P-MOS transistor and is grounded through the fifth resistor; a drain electrode D of the P-MOS transistor is connected with a current input end of the TEC control circuit and is meanwhile grounded through the second capacitor. Since the current buffer circuit consisting of the P-MOS transistor, the first capacitor, the second capacitor and the fifth resistor is low in component cost, the influence of surge current caused by the TEC control circuit on the electro-absorption modulated laser can be suppressed better, and the working stability of the laser is improved.

Description

technical field [0001] The invention relates to an electro-absorption modulated laser EML (Electro-absorption Modulated Laser), in particular to a TEC starting circuit of the electro-absorption modulated laser. Background technique [0002] In the long-distance transmission of SFP+ (Enhanced Small Form Factor Pluggable Module) and XFP (10 Gigabit Small Form Factor Pluggable Module) modules, it is necessary to use electro-absorption modulation lasers to meet the long-distance transmission performance. Since the output wavelength, current threshold, maximum output power and minimum power fluctuations of the EML laser are all affected by the operating temperature of the laser, a thermoelectric cooler TEC (Thermo Electric Cooler) and a high-precision negative temperature coefficient are integrated inside the EML laser. The thermistor NTC (Negative Temperature Coefficient) ensures that the laser works at a stable operating temperature point through a closed-loop feedback loop cir...

AI Technical Summary

Problems solved by technology

[0004] Since the first DC-DC circuit 21 and the second DC-DC circuit 22 inside the TEC control circuit 20 are hard-switched DC switching power supply circuits, and the load is a TEC31 with a DC resistance of only a few ohms, these internal circuits It will take some time from power-on to establishing a steady state, so a relatively large voltage difference will be generated at the moment of power-on to load on the TEC31 inside the laser 30, and the DC resistance of TEC31 is relatively small, so it flows through TEC31. The current will increase a lot in an instant, causing the module to generate a large inrush current at the moment of power-on, which seriously exceeds the performance requirements of SFP+ and XFP modules.

At present, the high-performance TEC control circuit 20 chip—the American company Maxim MAX8520 / MAX8521 chip is widely used in the industry. By artificially reducing the setting values ​​of the output current circuit 24 and the output voltage limiting circuit 25 inside the TEC control circuit 20, Even if the output voltage and current of the TEC control circuit 20 are both reduced, the inrush current generated at the moment when the module is powered on still cannot be suppressed

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