QSFP-40G-ER4-Arista-BCC | Arista Compatible 40GB Single-Mode ER4 Transceiver - 40km (40GBASE-ER4)

Q: Will this work in place of the Arista QSFP-40G-ER4?
A: Yes. This transceiver is a plug-and-play replacement for the Arista QSFP-40G-ER4. It meets the same IEEE 802.3ba 40GBASE-ER4 standard, uses the same QSFP+ form factor, and delivers the same 40 Gbps data rate over duplex single-mode fibre with CWDM wavelengths at 1271, 1291, 1311, and 1331 nm. The module will operate identically to the OEM part in any Arista 40G QSFP+ port.

Q: Which Arista platforms support this transceiver?
A: This transceiver works in any Arista switch or router with a QSFP+ port supporting 40GBASE-ER4 optics. According to Arista documentation, the QSFP-40G-ER4 is supported from EOS version 4.14.5 onwards. It is compatible with Arista 40G platforms that meet the QSFP+ MSA electrical interface specification and support the IEEE 802.3ba 40GBASE-ER4 standard.

Q: What fibre type and reach does this transceiver support?
A: This transceiver requires single-mode fibre (SMF), specifically ITU-T G.652 compliant OS2 cable. It supports transmission distances up to 40 km using four CWDM wavelengths multiplexed onto a single duplex LC fibre pair. For links shorter than approximately 10 km, optical attenuation may be required to prevent receiver damage from excessive input power.

Q: How does the four-lane CWDM architecture work in this module?
A: The module converts four independent electrical input lanes (each running at approximately 10.3125 Gbps) into four distinct CWDM optical wavelengths at 1271, 1291, 1311, and 1331 nm. An integrated optical multiplexer combines these four wavelengths onto a single transmit fibre strand. At the receiver end, a demultiplexer separates the four wavelengths and converts them back to four electrical lanes, delivering aggregate 40 Gbps throughput while using only two fibre strands instead of the eight required by parallel optics like 40GBASE-SR4.

Q: Can I monitor link health and optical parameters in real time?
A: Yes. The module supports digital diagnostics monitoring (DDM) accessible via the I2C serial interface as defined in the QSFP+ MSA specification. You can read real-time parameters including per-channel transmit optical power, per-channel receive optical power, module temperature, laser bias current, and supply voltage. These parameters allow proactive link quality monitoring, troubleshooting, and detection of degrading components before link failure occurs.