QSFP 40G SR4 Optical Transceivers for Highspeed Data Center Connectivity

The QSFP-40G-SR4 is a quad small form-factor pluggable optical transceiver built for 40 Gigabit Ethernet short-reach links, and has become a standard building block in high-speed data center networks. The module is designed to interconnect servers, switches and routers over multimode fiber at high bandwidth and short range. It packs four parallel 850nm channels into a single compact, hot-swappable package.

How the parallel optical design works

The module operates on parallel optical transmission. When an electrical signal enters the transceiver, an integrated four-channel array of 850nm vertical-cavity surface-emitting lasers (VCSELs) converts it into optical signals at high speed. Those signals travel across multimode fiber through an MTP/MPO interface. At the receiving end, a photodetector array restores the optical signals to electrical form, completing a bidirectional link.

By using a single wavelength of 850nm across stacked parallel lanes, the transceiver processes several optical channels simultaneously, which supports stable and efficient throughput. The design conforms to the IEEE 802.3ba standard and allows 4x10G breakout connections, giving network operators a degree of flexibility when migrating from 40G to 10G infrastructure.

Specifications at a glance

Rated at 40Gbps, the transceiver reaches up to 100 meters over OM3 multimode fiber and up to 150 meters over OM4, while drawing 1.5W of power. The principal technical parameters are summarized below.

Physical construction and monitoring

The module uses a compact housing with a 38-pin electrical interface. Internally it integrates electromagnetic interference shielding, the optical transceiver assembly, thermal management components and a digital optical monitoring (DOM) system. The DOM function allows network administrators to run real-time diagnostics and track optical power, temperature and other key metrics, which improves maintenance efficiency.

Because the unit is hot-swappable, it can be installed or replaced without interrupting network service, reducing downtime during equipment maintenance. It also carries FDA Class 1 laser safety certification and complies with the RoHS standard, supporting safe and environmentally compliant operation in data center environments.

Cabling and compatibility

Since the transceiver relies on four parallel optical lanes, it is paired with MTP/MPO trunk and harness cabling rather than duplex connectors. Deployment planning therefore centers on the fiber plant: OM3 cabling supports links of up to 100 meters, while OM4 extends the reach to 150 meters.

Frequently Asked Questions