A Brief Introduction on 4WDM (4 Wavelength Division Multiplexing)

With the rapid development of data centers and mobile base station, 100G optical transceivers are playing a more and more important roles in the data center construction and mobile backhaul. In order to meet the increasing needs for cost-effective and low-power 100G optical networks, 4WDM came out, which is a new module and cage/connector system that supports to transmit up to 40km. In this article, we will introduce you something about 4WDM that you may be interested in.

1. What Is 4WDM MSA

4WDM MSA (4 Wavelength Division Multiplexing Multi-Source Agreement) defines 4 x 25 Gbps Local Area Network Wavelength Division Multiplex (LAN- WDM) optical interfaces for 100G optical transceivers for Ethernet applications including 100 GbE. Forward error correction (FEC) is a link requirement in order to ensure reliable system operation. Two transceivers communicate over single mode fibers (SMF) of length from 2 meters to at least 20 or 40 kilometers. The transceiver electrical interface is not specified by this MSA but can have, for example, four lanes in each direction with a nominal signaling rate of 25.78125 Gbps per lane.

Different form factors for the transceivers are possible. The QSFP28 module is expected to be a popular form factor for these applications. Other form factors are possible and are not precluded by this MSA.

2. Introduction on 4WDM MSA Group

The 4WDM MSA Group is an industry consortium dedicated to defining optical specifications and promoting adoption of interoperable 100G (4x25G) optical transceivers for 10 km based on the CWDM4 wavelength grid, and for 20 km and 40 km based on the LAN-WDM wavelength grid, over duplex single-mode fiber (SMF). These extended reaches are important for modern data center interconnects and mobile backhaul applications. The 4WDM MSA Group is responding to previously unmet industry needs for longer reaches, lower costs, and lower power consumption as compared to previously available standards such that they are implementable in small form factors.

Members of the 4WDM MSA include Applied Optoelectronics, Broadcom, Brocade, Ciena, ColorChip, Dell, Finisar, Foxconn Interconnect Technology, Huawei Technology, Inphi, Intel, Juniper Networks, Kaiam, Lumentum, MACOM Technology, NeoPhotonics, Oclaro, Skorpios Technologies, Source Photonics, and Sumitomo Electric Industries.

3. 4WDM vs. CWDM4

4WDM MSA defines CWDM4 and 4WDM with different distances and wavelengths (2km/10km/20km/40km). 2km and 10km use CWDM wavelength. 20km and 40km use LAN WDM wavelength.

With the different size of the CWDM and LAN WDM wavelengths, the wavelength-transmitting TOSA for LAN WDM must be carried with a TEC (Thermo Electric Cooler). As the stable wavelength drifts with temperature, TEC consumes an extra 0.5W of power, so the overall power consumption of optical transceivers with LAN WDM wavelengths will be higher than that of CWDM optical transceivers.

4. 100G QSFP28 4WDM 40KM

100G QSFP28 4WDM 40KM is a 100Gb/s transceiver module designed for optical communication applications compliant to QSFP28 4WDM 40KM MSA standard. The module converts 4 input channels of 25Gb/s electrical data to 4 channels of LAN WDM optical signals and then multiplexes them into a single channel for 100Gb/s optical transmission. Reversely on the receiver side, the module de-multiplexes a 100Gb/s optical input into 4 channels of LAN WDM optical signals and then converts them to 4 output channels of electrical data. Ethernet applications are up to 30km links without FEC and up to 40km links with FEC interconnections.

Main Features:

  • 4 channels full-duplex transceiver modules
  • Supports data rate up to 103.1Gb/s
  • Supports QSFP28 4WDM 40km MSA
  • 4 x 25Gb/s DFB-based LAN-WDM Cooling transmitter
  • 4 channels APD ROSA
  • Internal CDR circuits on both receiver and transmitter channels
  • Low power consumption <4.2W
  • Hot Pluggable QSFP form factor
  • Up to 30km reach for G.652 SMF without FEC
  • Up to 40km reach for G.652 SMF with FEC
  • Duplex LC receptacles
  • Built-in digital diagnostic functions
  • Operating case temperature 0°C to +70°C
  • 3V power supply voltage
  • RoHS 6 compliant(lead free)


With the advantages of cost-effectiveness, low power consumption as well as long transmission distance, we can look forward that 100G QSFP28 4WDM will have a good performance on 100G optical networks. Gigalight recently released the latest 100G QSFP28 4WDM optical transceiver supporting 100GE applications. For more product details, welcome to visit our official website.

About Gigalight:

Gigalight is a design innovator in global optical interconnect field. A series of optical interconnect products include: optical transceivers, passive optical components, active optical cables, GIGAC MTP/MPO cablings, and cloud programmers & checkers, etc. Three applications are mainly covered: Data Center & Cloud Computing, MAN & Broadcast Video, and Mobile Network & 5G Optical Transmission. Gigalight takes advantage of its exclusive design to provide clients with one-stop optical network devices and cost-effective products.