I’d like to explain the practical relationship between optical networks and 5G.
Fronthaul and Optical Transport in 5G
In 5G, we use CWDM (Coarse Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing) for high-capacity, low-latency transport links. These technologies connect the radio part of Open RAN to the cloud infrastructure.
C-RAN and Fronthaul Transmission
5G networks implement C-RAN (Cloud Radio Access Network), which splits the RAN into three main components:
- RU (Radio Unit) – Handles radio transmission and reception.
- DU (Distributed Unit) – Processes lower-layer protocols.
- CU (Centralized Unit) – Manages higher-layer network functions.
The fronthaul is the optical transmission link that connects the RU to the DU and CU using CWDM or DWDM. It enables multiple optical carriers with different wavelengths to be transported over a single fiber.
CWDM vs. DWDM in Fronthaul
- CWDM supports 2 to 8 channels, making it suitable for short- to medium-range connections.
- DWDM provides higher capacity, allowing for more wavelengths over the same fiber, ideal for high-density networks.
Signal Flow in 5G Transport
- The mobile station sends traffic to the base station, which is received by the antenna array.
- The signal is processed by the RRH (Remote Radio Head), responsible for amplification and modulation.
- The optical module converts the electrical signal into an optical signal.
- The signal is then mapped onto CWDM or DWDM wavelengths using fronthaul transport devices.
- The traffic flows from the DU to CU via the midhaul and then to the core network via the backhaul.
By leveraging CWDM and DWDM, 5G networks achieve high-capacity, low-latency connectivity between distributed and centralized units, ensuring efficient data transport.
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