Does the RRU s optical module emit light

Yes, the RRU's optical module emits light through its transmitter optical sub-assembly (TOSA) to send data to the BBU.

How the Optical Module Works

The optical module in an RRU contains two main components: the Transmitter Optical Sub-Assembly (TOSA) and the Receiver Optical Sub-Assembly (ROSA). The TOSA is responsible for emitting light, converting electrical signals from the RRU into optical signals that travel through fiber optic cables to the Baseband Unit (BBU) or other network equipment . This light is typically generated by a laser diode (LD) or, in some cases, a light-emitting diode (LED), which is modulated according to the data being transmitted .

The TOSA also includes an automatic optical power control (APC) circuit to maintain a consistent output power, ensuring reliable signal transmission over the optical fiber . The ROSA, on the other hand, receives incoming optical signals and converts them back into electrical signals for processing by the RRU .

RRU Optical Module in Practice

In Huawei RRUs, such as the RRU3953 and RRU5517t, the optical module is used to establish a CPRI (Common Public Radio Interface) link between the RRU and the BBU . The module's light emission is essential for transmitting downlink baseband data from the BBU to the RRU and for sending uplink data from the RRU back to the BBU. Indicators on the RRU panel can show the status of the optical module, including whether it is transmitting or receiving signals properly .

Safety Note

Because the optical module emits laser light, it is important not to look directly into the fiber or the module's optical port, as the laser can be harmful to the eyes. Proper handling and installation by trained personnel are recommended .

In summary, the RRU's optical module does emit light via its TOSA to transmit data over fiber optics, forming a critical part of the RRU-BBU communication link in modern wireless networks.