This article briefly introduces the application scenarios of QSFP-DD in data centers—mid-range transmission.

QSFP-DD Mid-Range Optical Modules

There are various types of QSFP-DD optical modules for 2km-10km transmission.

The main focus is on four models: FR4/FR8 (2km) and LR4/LR8 (10km).

QSFP-DD FR4 Optical Module

The "FR" in QSFP-DD FR4 optical module denotes a transmission distance of 2km. It employs four non-cooled EML lasers with CWDM wavelengths, achieving a single-wave rate of 106.25Gbps based on PAM4 modulation. These signals are multiplexed and coupled into a single-mode fiber (SMF) for transmission, with a maximum transmission distance of up to 2km via SMF.

QSFP-DD FR8 Optical Module

Similar to FR4, the "FR" in QSFP-DD FR8 optical module denotes a transmission distance of 2km. It uses eight DML lasers with LWDM wavelengths, achieving a single-wave rate of 50G PAM4. These signals are multiplexed and coupled into a single-mode fiber (SMF) for transmission, with a maximum transmission distance of up to 2km via SMF.

QSFP-DD LR4 Optical Module

The "LR" in QSFP-DD LR4 optical module denotes long-distance transmission of 10km. It utilizes four EML lasers with CWDM wavelengths (5nm wavelength spacing, requiring a TEC cooler to control temperature) and achieves a single-wave rate of 106.25Gbps based on PAM4 modulation. These signals are multiplexed and coupled into a single-mode fiber (SMF) for transmission, with a maximum transmission distance of up to 10km via SMF.

QSFP-DD LR8 Optical Module

Similar to LR4, the "LR" in QSFP-DD LR8 optical module denotes long-distance transmission of 10km. It uses eight DML lasers with LWDM wavelengths and achieves a single-wave rate of 50Gbps based on PAM4 modulation. These signals are multiplexed and coupled into a single-mode fiber (SMF) for transmission, with a maximum transmission distance of up to 10km via SMF.

Additional Learning Hub Resources

Differences between SFP-10G-LRM and SFP-10G-LR Optical Modules 

40G QSFP+ AOC Active Optical Cable Overview 

QSFP Bidi Optical Module Overview