DSFP Optical Module Packaging for 5G Fronthaul
Dec 06, 2025|
What is DSFP?
Simply put, it means that in the same SFP28 packaged optical module, twice the density can be achieved：
| Abbreviation | English Full Name | Channel Description |
|---|---|---|
| SFP | Small Form-factor Pluggable | One channel (1× TX+RX) |
| DSFP | Dual Small Form-factor Pluggable | Two channels (2× TX+RX) |
One of the goals of this MSA protocol is to achieve double the density for 5G fronthaul within the same SFP28 package.
Although DSFP and SFP have the same form factor, they differ in the number of gold fingers.
| Type | English Full Name | Number of Electrical Pins (on the connector) |
|---|---|---|
| SFP | Small Form-factor Pluggable | 20 |
| DSFP | Dual Small Form-factor Pluggable | 22 |
The DSFP adds two more pins to the original SFP's 20 pins.
The DSFP PCB resin is transparent, with the 21st and 22nd gold fingers marked in dark.
The side cross-sectional view of the gold fingers shows two pairs of differential signals, allowing one optical module to transmit and receive two 25G signals in 5G fronthaul.
Complete 22 pin definitions：
Regarding 5G fronthaul Open-WDM semi-active and colored light modules
In 5G, fronthaul refers to the distance from DU to AAU. Typically, the transmission distance of the optical module in the C-RAN fronthaul access method is 5-10km.
Typically, a single DU connects to 6-10 AAUs (see diagram below).
Each base station requires antennas to cover 360°. The simplest configuration is 3 antennas per AAU, with each antenna responsible for a 120° sector. Therefore, each AAU requires 3 pairs of optical modules for signal transmission.
3 pairs of modules, 3 sets of transceiver modules.
If gray light is used, that is, a module with the same wavelength, then there are 6 optical fibers from the node to the antenna, and the same number of optical fibers from the node to the DU.
This is the legendary 5G fronthaul, fiber optic direct drive solution.
If deploying fiber optic cables becomes more difficult, reducing the number of fibers and increasing the complexity of the optical modules is one possible approach.
For example, BiDi (single-line, bidirectional), with a pair of modules sharing a single fiber for transmission and reception, using two wavelengths for differentiation.
This saves half the fiber optic resources.
China Mobile's proposed color-coded optical fiber solution can save more fiber optic cable, but the trade-off is that the optical modules will be more difficult to implement.
It involves one base station, three pairs of modules, using six wavelengths multiplexed, and transmitting data through a single optical fiber.
This 6-wavelength multiplexing method uses an active node and active wavelength division multiplexing (WDM) device at the DU input end; at the base station side, it uses passive AWG multiplexing/demultiplexing to supply the transmission and reception of the three modules, for a total of six wavelengths.
This colored optical fronthaul scheme uses one active node and one passive node, which China Mobile calls "semi-active."
These three access methods-direct drive, BiDi, and semi-active colored light-have different requirements for optical modules.
Colored light modules require six wavelengths, with the low-dispersion band being the 0 band. In the mature 100G (4 wavelengths × 25G) industry chain of data centers, 25G lasers can be found in the 1271, 1291, 1311, and 13314 bands.
As for the other two wavelengths, how to choose them is still under discussion among several equipment manufacturers.
One suggestion is to add two new wavelengths.
Another approach is to insert wavelengths, shortening the 20nm wavelength interval to 10mm and expanding it to 12 wavelengths (Kuang Guohua added in 2021, and the scheme of adding two new wavelengths was later selected, and the scheme of inserting wavelengths was no longer used).