Can the 400G-FR4 and 400G-LR4 Transceivers Interoperate with Each Other?

Picture of Harper Ross

Harper Ross

Answered on 1:59 am

Yes, the 400G-FR4 and 400G-LR4 transceivers can interoperate up to a reach of 2km (limited by the FR4). Note that max allowed Receiver power for the 400G-FR4 (max Rx power of 3.5dBm) may require a minimum level of attenuation to be present if connected to a 400G-LR4 transmitter (Max Tx power of 5.1dBm).

According to the Cisco 400G QSFP-DD Cable and Transceiver Modules Data Sheet, the 400G-FR4 and the 400G-LR4 transceivers are both compliant to the 100G Lambda MSA standard, which defines a common optical interface for 100G per wavelength applications. The 400G-FR4 and the 400G-LR4 transceivers use four optical lanes, each carrying a 100G PAM4 signal, over a duplex LC single-mode fiber. The main difference between them is the transmission distance: the 400G-FR4 can reach up to 2km, while the 400G-LR4 can reach up to 10km.

Therefore, to interoperate these transceivers, they need to have compatible wavelengths, power budgets, and dispersion compensation. The 100G Lambda MSA specifies two sets of wavelengths for 100G per wavelength applications: LAN-WDM (1295.56nm, 1300.05nm, 1304.58nm, and 1309.14nm) and CWDM4 (1271nm, 1291nm, 1311nm, and 1331nm).

People Also Ask

USFP vs CPO: Pluggable vs Co-Packaged Optics Compared

USFP vs CPO is a choice between two ways to move data inside an AI data center. USFP (Ultra-Dense Small Form Factor Pluggable) is a pluggable 400G-per-lane optical module you can swap in the field. CPO (co-packaged optics) integrates the optical engine directly into the switch chip to save power, at the

DWDM OADM: Passive Add-Drop Modules Explained

Every DWDM OADM a wavelength passes through introduces some optical loss. Across five cascaded nodes, that loss can consume a substantial share of the link budget—potentially comparable to tens of kilometers of fiber, depending on the OADM design. That is a detail an initial network plan can easily overlook. It

MikroTik CRS804-4DDQ Review: The $1,100 400GbE Switch That Changes the Math

Four 400G ports, 1.6 Tbps of aggregate one-direction port bandwidth, and a compact chassis at an unusually accessible price. The hardware is compelling; optical interconnect costs can determine the total budget. Four 400GbE ports delivering 1.6 Tbps of aggregate one-direction port bandwidth, in a half-width chassis you can lift with

USFP vs OSFP vs QSFP-DD: Form Factors Compared

The three high-density pluggable form factors relevant to 400G, 800G, and next-generation AI networks are QSFP-DD, OSFP, and the newly announced USFP design. QSFP-DD offers broad backward compatibility with supported legacy QSFP modules, OSFP provides a larger form factor with integrated heatsink options and support for higher-power module generations, and

DWDM Channels Explained: ITU Grid, Spacing & Channel Plans

Two DWDM transceivers can both be labeled “channel 29” and still fail to establish a link. The channel label does not uniquely identify the optical frequency. Different vendors may use different numbering conventions, while the transceivers and filters must operate at compatible frequencies for the link to work. If you’ve

Related Articles

800g sr8 and 400g sr4

800G SR8 and 400G SR4 Optical Transceiver Modules Compatibility and Interconnection Test Report

Version Change Log Writer V0 Sample Test Cassie Test Purpose Test Objects:800G OSFP SR8/400G OSFP SR4/400G Q112 SR4. By conducting corresponding tests, the test parameters meet the relevant industry standards, and the test modules can be normally used for Nvidia (Mellanox) MQM9790 switch, Nvidia (Mellanox) ConnectX-7 network card and Nvidia (Mellanox) BlueField-3, laying a foundation for

Read More »
USFP vs CPO

USFP vs CPO: Pluggable vs Co-Packaged Optics Compared

USFP vs CPO is a choice between two ways to move data inside an AI data center. USFP (Ultra-Dense Small Form Factor Pluggable) is a pluggable 400G-per-lane optical module you can swap in the field. CPO (co-packaged optics) integrates the optical engine directly into the switch chip to save power, at the

Read More »
DWDM OADM

DWDM OADM: Passive Add-Drop Modules Explained

Every DWDM OADM a wavelength passes through introduces some optical loss. Across five cascaded nodes, that loss can consume a substantial share of the link budget—potentially comparable to tens of kilometers of fiber, depending on the OADM design. That is a detail an initial network plan can easily overlook. It

Read More »
USFP vs OSFP vs QSFP-DD

USFP vs OSFP vs QSFP-DD: Form Factors Compared

The three high-density pluggable form factors relevant to 400G, 800G, and next-generation AI networks are QSFP-DD, OSFP, and the newly announced USFP design. QSFP-DD offers broad backward compatibility with supported legacy QSFP modules, OSFP provides a larger form factor with integrated heatsink options and support for higher-power module generations, and

Read More »
DWDM channels

DWDM Channels Explained: ITU Grid, Spacing & Channel Plans

Two DWDM transceivers can both be labeled “channel 29” and still fail to establish a link. The channel label does not uniquely identify the optical frequency. Different vendors may use different numbering conventions, while the transceivers and filters must operate at compatible frequencies for the link to work. If you’ve

Read More »
Scroll to Top