Kyoto Semiconductor develops photodiode with 400Gbps transmission speed

Kyoto Semiconductor has developed a high-speed photodiode KP-H KPDEH12L-CC1C to support 400Gbps transmission systems that use PAM4 (Pulse Amplitude Modulation 4) inside and between data centers.

With the introduction of this InGaAs photodiode, the company is continually supporting the increasing speeds and capacity requirements for transmission systems in 5G networks and beyond. Mass production will start in November, 2020.

High-speed

The size of the carrier on which the PD is mounted, and the width and length of the high frequency electrode pattern placed on the carrier are optimized using an electromagnetic simulation (Note 2).

As a result, we have achieved the world’s top class 400Gbps and 40GHz as a frequency band with an integrated transimpedance amplifier. The KP-H photodiode has passed Telcordia GR-468-Core, which is the standard reliability test for communication equipment.

Easy implementation

KPDEH12L-CC1C is mounted on a carrier that is optimally designed to achieve high frequency. A condenser lens is integrated on the backside of the photodiode (Note 3), allowing the incoming light to collect in the light absorption area, and makes it easy to align the optical fiber with PD. The PD chip is mounted on a carrier twice as big as the chip itself.

Background of development

Currently, we have achieved transmission speeds of mainly 100Gbps by bundling 4 lanes of 25Gbps. However, there are growing demands in the market for 400Gps to 800Gbps transmission speeds.

The Institute of Electrical and Electronics Engineers (IEEE) set the standard of PAM4 that corresponds with 4-bit signal to one modulation. The transmission speed per PD reaches 50Gps (= 400Gps/4 lanes/2 (PAM4)). The transmission bandwidth required for the PD to achieve this speed will be 35~40GHz.