What is RF-over-fiber?

PPM has developed technology for converting an RF signal into an optical signal for transmission over optical fiber, and converting it back into an RF signal. A typical system will consist of three main elements: an optical transmitter, a fiber optic cable and an optical receiver.

The system is defined in terms of normal RF parameters i.e. gain, noise figure, linearity etc., and can be treated as an RF black box by a systems designer.

The RF-over-fiber systems generally use intensity modulation. This may be thought of as amplitude modulation in the optical domain. The RF signal applied by the user to the optical transmitter, is used to directly modulate the intensity of a light source (e.g. a laser diode). There is no frequency conversion or analog-to-digital conversion involved. This technique results in the widest possible frequency response and highest possible dynamic range. At the optical receiver, the intensity modulated light is converted back into an RF signal using a high frequency photodiode.

Intensity modulation places very demanding requirements on all components in the optical path - particularly the laser diode. In PPM's products, these components have been designed for optimum efficiency, noise and linearity performance.

What is RF-over-fiber?

Optical fiber is small in size, flexible, very low loss and is a very well established technology. It offers a number of inherent advantages over the use of coaxial cables or free-space transmission, including:

• Very low loss (less than 0.5dB signal loss per km!)
• Non-conductive medium, resulting in electrical isolation for safety and interference.
• Immunity to electrical interference.
• Easy deployment due to small size and flexibility of the rugged cable.

PPM's ViaLite Fiber Optic Systems offer unbeatable advantages for the transmission of analog, RF and digital data signals over optical fiber, and are used for the replacement of conventional coaxial cable in many different applications.

The wide dynamic range, broadband ViaLite fiber optic link technology supports the transmission of data of any modulation type with minimal degradation.

A diverse range of applications is catered for by products optimised for specific applications including: teleports, satellite ground stations, Satellite downlink, L band fiber, interfacility linking, IF to fiber, 70 140, cellular networks, antenna remoting, fibre optic modem, GPS timing and TV broadcast signal distribution.