These technical specifications define an 8 x 50 Gb/s Coarse Wavelength Division Multiplexing (CWDM) optical interface for 400 Gb/s optical transceivers for Ethernet applications including 400 Gigabit Ethernet. Two optical transceivers implementing this interface can communicate over single mode fibers (SMF) of length from 2 meters up to 2 kilometers. The transceiver electrical interface is not specified in this document but can have, for example, 8 lanes in each direction with a nominal signaling rate of 53.125 Gb/s per lane.
Different form factors for the transceivers are possible. Common implementations at the time of this writing are expected to include QSFP-DD and OSFP pluggable optical transceivers as well as COBO on-board optical transceivers. Other form factors are possible and are not precluded by these specifications.
CWDM8 Optical Specifications
.Optical Wavelengths
The wavelength range for each lane of the 400G CWDM8 optical transceiver is defined in Table 1. The center wavelengths are spaced at 20 nm.
Lane Center Wavelength Wavelength Range
L0 1271 nm 1264.5 to 1277.5 nm
L1 1291 nm 1284.5 to 1297.5 nm
L2 1311 nm 1304.5 to 1317.5 nm
L3 1331 nm 1324.5 to 1337.5 nm
L4 1351 nm 1344.5 to 1357.5 nm
L5 1371 nm 1364.5 to 1377.5 nm
L6 1391 nm 1384.5 to 1397.5 nm
L7 1411 nm 1404.5 to 1417.5 nm
Optical Specifications
The operating range for a CWDM8 transceiver is defined in Table 2. A CWDM8 compliant PMD operates on single-mode fibers according to the specifications defined in Table 8 and characteristics in Table 9. A PMD that exceeds the required operating range while meeting all other optical specifications is considered compliant (e.g., operating at 3 km meets the operating range requirement of 2 m to 2 km).
Module type Required operating range
400GE-CWDM8-2 2 m to 2 km
CWDM8 2 km Interface, Illustrative Link Power Budget
An illustrative power budget and penalties for CWDM4 are shown in following Table.
Description Value Unit
Power budget (for max TDEC) 6.8 dB
Operating distance 2 km
Channel insertion loss(a) 4 dB
Maximum discrete reflectance(b)-35 dB
Allocation for penalties (for max TDEC) 2.8 dB
Additional insertion loss allowed 0 dB
(a) Includes 0.1dB MPI penalty
(b) Assumes 6 connectors in the link
