Feature: Thermal management


Fgure 4: 1550nm DFB optical spectra at 40mA for varying temperatures


Figure 5: Lifetime vs TEC power


especially within AI, cloud and telecom networks requires precise engineering in both device thermal management and supporting control systems. T ere’s a rule of thumb that states keeping the junction temperature in the 20-35°C band with tight control (±0.1°C) preserves wavelength stability and coupling and dramatically extends mean time before failure (MTBF).


Temperature and wavelength control T e most direct infl uence on a laser diode’s emission wavelength is temperature, which aff ects both the refractive index and the physical dimensions of the semiconductor material. For example, in distributed feedback (DFB) lasers, the emission wavelength shiſt s by approximately 0.1nm per °C; see Figure 4. In dense wavelength-division multiplexing (DWDM) systems, where channel spacings are 0.4-0.8nm, this sensitivity means that even small temperature excursions can cause the laser to driſt out of its specifi ed wavelength, leading to crosstalk, degraded system


32 November 2025 www.electronicsworld.co.uk


performance and reliability issues. For high-performance telecom modules, stabilising the


wavelength within 0.01nm is oſt en required, achievable only with robust thermoelectric cooler (TEC) control; see Figure 3. TECs serve as the foundation for precise thermal stabilisation. T ey hold the laser assembly at a fi xed setpoint, typically 20-35°C.


Design trade-off s: Reliability vs power consumption Lower junction temperatures reduce the required drive current, lower non-radiative recombination and decrease dark current, all of which improve performance, increase device reliability and result in longer device operating life; see Figure 5. However, lower setpoints increase the TEC’s power draw, impacting overall system effi ciency and operating costs, especially when scaled to hyperscale data centres. T ere is an inherent trade-off between TEC power consumption and laser diode longevity. Running the laser junction cooler


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