Optical Transceivers Overcome Heat

The rapid development of AI and large language models has led to a surge in demand for high-speed optical transceivers in data centers and AI cluster computers. As optical transceiver speeds scale from 100 Gbps (for entry-level data center applications) to 400 Gbps (widely used in current AI clusters), to 800 Gbps (preferred for high-demand applications), to over 1.6 Tbps (supporting next-generation AI workloads), efficient thermal management is critical to ensure performance, reliability, and energy efficiency.

As the transmission distance increases, the transceiver’s need for temperature stability becomes more critical. Optical transceivers, especially long-distance ones, require precise temperature control to maintain laser stability and performance.

Optical transceivers rely on laser diodes for data transmission. These lasers are sensitive to temperature changes, which can cause signal degradation and reduced reliability. Optical transceiver manufacturers face several thermal challenges due to current AI and data center activities:

• Transceiver power requirements continue to increase

• Transceiver size is limited

• Transceiver thermal limit approaches

• Signal-to-noise ratio ratio budget keeps tightening as speed increases from 400G to 3.2T

• Cooling and temperature stability are required

• All components need to save power

Precise thermal control is critical to maintaining optimal performance of the laser diode and the entire optical transceiver.

The performance of a laser diode is affected by various factors, including temperature, current, and optical power. Temperature changes can affect the electrical and optical characteristics of a laser diode and affect its performance and lifetime. Out of the maximum operating range, performance degrades due to increased thermal resistance and reduced current gain. At the same time , high temperatures can cause the wavelength of laser diodes to change, affecting performance and reliability.

Wavelength variations can cause severe crosstalk or even laser diode failure.

For example, DFB laser diodes typically emit light at a wavelength of approximately 1260 to 1650 nm. An increase in temperature causes a shift in the peak wavelength of approximately 0.1 nm/°C. TECs provide reliable temperature stability by effectively dissipating heat and maintaining a stable thermal environment. This improves signal integrity and extends the life of the optical transceiver.

Another problem with temperature fluctuations is crosstalk. This is seen in long-distance communication links and the ones that require high bandwidth. Hyperscale data centers are one example where optical transceivers use wavelength division multiplexing to increase data throughput within optical fibers by combining multiple data streams in parallel.

Advances in laser diode technology also require advances in thermal management solutions. As data throughput speeds increase and the distance between connection points increases, laser diodes generate more heat, so laser diode packages require higher heat pumping capabilities to move heat away from the sensitive electronics and out of the package.

To pump the heat out, micro-TECs with higher fill factors and thinner profiles are needed to improve efficiency and maintain precise wavelength control and temperature stability. The reason for using micro TEC is due to its several advantages as follows:

• Smaller size

• Respond to temperature changes more effectively

• Improve the performance and reliability of laser diodes

• Cost-effective manufacturing

• Suitable for mass production

• Reduce power consumption

New thermoelectric materials and high-precision manufacturing processes have enabled the development of micro-TECs with smaller form factors. This allows the laser diode to be made into a smaller form factor without compromising thermal stability. They can also respond more efficiently to temperature changes, which is important for optical communications systems. Higher efficiency can improve the performance and reliability of laser diodes, thereby enabling higher data transmission rates. In addition, high-throughput, low-cost manufacturing of micro-TECs helps reduce the overall cost of laser diode systems.

Micro-TECs, such as Laird’s new OptoTEC MBX series, are designed specifically for laser diode temperature stabilization (see Figure 2). The ultra-compact MBX series meets the requirements of modern laser diode applications, with smaller size, lower power consumption, higher reliability and lower-cost mass production. These factors can improve the performance and extend the reliability of laser diodes, thus enabling innovation in next-generation telecommunication applications.

OptoTEC MBX Series

As optical transceivers evolve, TEC suppliers are designing smaller, thinner, and more form-fitting modules to fit into these compact geometries without sacrificing performance (see below).

Application example：800g transceiver TECs

Key design consideration for micro-TECs include:

• Sufficient cooling capacity

• Can handle optical transceiver ranging from 1 to 3W

• Compact size

• Fits into transceiver modules while providing efficient cooling

High-volume manufacturing simplifies scalable manufacturing and assembly processes, helping to reduce production costs and increase yields – ensuring that TECs can be produced reliably and economically for large-scale deployment.

As artificial intelligence continues to drive demand for faster and more efficient data transmission, the optical transceiver market is expected to continue to grow and innovate. Customized thermoelectric cooling solutions will play a critical role in the rapidly evolving AI and data center technology environments, ensuring the performance and reliability of these critical components.