Objective   As the communication rate increases, the power consumption of optical modules increases. Therefore, the heat dissipation environment of optical modules must be ensured. In order to ensure that the optical module can still maintain good performance under extreme environment, it is necessary to add extreme temperature cycle experiment in the delivery test of the optical module. With the increasing demand for optical modules, improving the efficiency of optical module delivery test has become the first engineering problem to be solved. Therefore, the design of the thermal control system for the high-speed communication optical module is important.

  Methods  First, according to the characteristics of the semiconductor cooler, the thermoelectric cooler assembly of the device under test was designed (Fig.3-4) and the results of Foltherm simulation indicate the availability of thermoelectric refrigeration components (Fig.6-7). Then, according to the principle and characteristics of the semiconductor refrigerator, the heat dissipation system is designed (Fig.17-19). Finally, the temperature control efficiency and the effect of the thermal control system and the water cooler are compared.

  Results and Discussions   The thermal control system of high-speed communication optical module uses a semiconductor cooler as the refrigeration unit, and the rise and fall time of the optical module in QSFP-DD packaging mode can be controlled within 110 s (Tab.11 and Fig.24). The rise and fall time of the optical module in QSFP-28 encapsulation mode can be controlled within 60 s (Tab.11 and Fig.25). The effect of temperature control is good, and the high-speed communication optical module manufacturers can analyze the performance of the optical module within the operating temperature range of commercial grade. The system is mainly composed of the device under test, thermoelectric cooler, the fixture, the controller of the semiconductor cooler and the heat dissipation system. Among them, the thermoelectric cooler assembly of the device under test is made up of the cylinder bracket and the cold plate radiator mounting box, which effectively reduces the heat leakage (Fig.3-4); Flotherm software is used to establish a thermal simulation model of cold plate heat exchanger in thermoelectric refrigeration components. The simulation results show that the module shell temperature can be stabilized at −0.382 ℃, and the cold plate heat exchanger can meet the requirements (Fig.6-7). And in the meantime, Flow Simulation is adopted to optimize the water flow of the cold plate heat exchanger in the heat dissipation system. The flow velocity of the optimized water flow in the cold plate heat exchanger is greater than 0.02 m/s (Fig.14), and the optimized water structure is available. This system has the advantages of little vibration and low noise, and only one-third volume of the water cooler (Fig.20). Meanwhile, this thermal control system basically meets the temperature control requirements for the high-speed communication optical modules with the common packaging methods.

  Conclusions   The time of temperature control of the optical module with the thermal control system is 10 s longer than that with the water cooler. But it has the advantages of miniaturization, low noise and zero vibration, which is more conducive to the integrated testing of optical modules. Using this system can not only test the optical modules in the QSFP-DD package mode independently, but also realizes the dual-channel parallel test of the optical modules in the QSFP-28 package mode to double the test efficiency of optical module.