RFoF transceiver is the combination of RF to optical converter with transmitter and receiver. RFoF (RF to optical) transmitter is used to convert RF and microwave signals to equivalent optical signals to carry over long distances through fibre optic cable. On the other end, the Optical receiver converts the received optical signal back to an equivalent RF signal.
RF over Fiber modules (RFoF) is used in satellite communication, GPS signal distribution, long-distance data transmission etc, as it is a very easy and cost-effective solution.
To learn about RF and Microwave communication systems from the best books, we recommend checking the following article.
To understand the RFoF Transceivers in a better way, we recommend understanding the following components, which are used along with RF over Fiber Transceivers.
In this RFoF Transceiver article, we will cover,
The primary requirement of RF over Fiber modules is to replace coaxial cables with optical cables for low loss transmission of RF signal for long distances. The prime elements of an RFoF communication link is an Optical Transmitter, fibre Optic Cable, and Optical Receiver.
In the transmitting station, the RF to optical converter converts the RF signal to an optical signal whose amplitude is proportional to the input RF signal level and is transmitted through the fibre channel to long-distance with negligible loss. The Optical Receiver receivers at the other end of the optical cable will receive the signal and converts it back to an original RF signal.
The RF over Fiber modules is used for the applications like SATCOM, Radars, VSAT gateways etc. where data need to transmit to long-distance with very lower loss.
Now many manufactures introduce variable bidirectional RFoF Transceivers to use a single optical fibre cable for the uplink and downlink (transmission and reception) of the signal.
Variable bidirectional RFoF Transceivers have bidirectional (2 way) RF over Fiber transceiver which can convert RF signal to optical and optical signal to RF without interfering with each other. These bidirectional RFoF Transceivers are mainly used where transmission and reception of the signal are needed. The RF over fibre link is implemented by deploying one bidirectional RFoF Transceivers at station one and the other at another station.
These transceivers use WDM technology to send and receive optical signals using only one fibre link between the TxRx stations. In the advanced versions, internal amplifiers, gain control units and control cards for remote management will be available.
The basic application of an RFoF transceiver is in an RF communication system to transmit RF signals consisting of data, video etc over a long distance without loss. Another prime application is the development of the programmable RF delay lines, which have many applications in the test and measurement industry. Below is the listed industrial application of RFoF modules.
When selecting an RFoF Transceiver for the communication system design, frequency and conversion accuracy are the prime features that need to consider. In addition, the following specification of an RFoF Trans-receiver needs to match for the perfect design of the overall communication system.
The frequency range of the RFoF Trans-receiver is the range of frequency it can convert for transmitting and receiving. In general, RFoF Tx/Rx modules are tuned for the specific frequency of operation even though wideband frequency modules are available in the market.
Gain flatness indicates the variation in the output power level over the frequency band of operation. The Gain flatness within +/- 1 dB over the entire band of frequency operation is acceptable in communication systems.
Noise Figure of RFoF Transceivers indicates the amount of noise generated inside the Transceiver modules. Lowering the noise figure better the RFoF modules as higher noise will affect the quality of the original signal.
Input put and output VSWR of the RFoF transceivers need to match with the RF source at the transmit side and RF receiver at the receiver side to avoid the reflection of the signal.
The sensitivity of the RF to optical converter is the minimum required signal power level to convert the received signal to optical signal for transmission. The higher the sensitivity (Capability to convert very low signal) is better the performance of the RFoF transmitter.
The output power of the RF signal at the optical to RF converter indicates the power level it can generate using an internal amplifier and provided to the RF receiver chain at the receiver station. Required power level output from the RFoF module helps to avoid the requirement of further amplifiers. Now in advance RFoF transceivers, there are options available to control the output power and gain.
As RF over fiver transceiver consists of many active components for the conversion and the amplification, power consumption of these modules needs to be optimized as per the system requirement.
RF over Fiber transceivers are available with different packages like modules, bend top standalone units, 19-inch rack assemble with various RF and optical connector options. The system integrates can select the modules or the units as per the overall design requirements.
As these RF over fibre modules need to fix up with the external units like antenna hub, environmental properties like humidity, water resistance, operating temperature etc need to match to the environment it is expected to operate.
Now RFoF links are getting more applications as it is a very cost-effective and reliable solution. Most of these RF over fibre links can theoretically operate for applications, such as SATCOM, GPS, DAS, and many other communication systems.
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