Radio Over Fiber


RADIO OVER FIBER

(RoF)

Radio over Fiber (ROF) is refers to a technology where, light is modulated in radio frequency and transmitted over optical fiber to facilitate wireless access. Although RF transmission over fiber is done in many occasions such as in Cable TV (CATV) networks and in Satellite base stations, the term ROF is usually applied when this is done for wireless access. RoF technology is a technology by which microwave (electrical) signals are distributed by means of optical components and techniques. A RoF system consists of a Central Site (CS) and a Remote Site (RS) connected by an optical fiber link or network. If the application area is in a GSM network, then the CS could be the Mobile Switching Centre (MSC) and the RS the base station (BS) for wireless Local Area Networks (WLANs), the CS would be the headed while the Radio Access Point (RAP) would act as the RS.

The Radio over Fiber System Concept (Broadband radio hand)

WHY RADIO OVER FIBER?

Optical fiber is small in size, flexible. very low loss and is very well established technology .it offer a number of inherent advantages over the use of coaxial cable or free transmission, including :

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

RF-over fiber links offer unbeatable advantages for the transmission of analog ,RF and digital data signals over the use  optical fiber , and are used for the replacement of conventional coaxial cable in many different applications.

BENEFIT OF RADIO OVER FIBER SYSTEMS?

  1. Low Attenuation Loss
  2. Large Bandwidth
  3. Immunity to Radio Frequency Interference
  4. Easy Installation and Maintenance
  5. Operational Flexibility
  6. Reduced Power Consumption
  7. Millimeter Waves
  8. Radio System Functionalities

Combination of DWDM and RoF transmission

Radio over Fibre link more closer :

There are two types of Modulation in that link :

1. Baseband-RF Modulation

  • Typical digital wireless modulation schemes (QPSK, GMSK or QAM)
  • Decided by the wireless system operator
  • ROF engineer usually don’t have control

2. RF-Optical modulation

  • ROF engineer have control
  • Direct or external modulation
  • Intensity or coherent modulation

APPLICATIONS OF RADIO-OVER-FIBER TECHNOLOGY

The field of mobile networks is an important application area of RoF technology. The ever-rising number of mobile subscribers coupled with the increasing demand for broadband services have kept sustained pressure on mobile networks to offer increased capacity(5). Therefore, mobile traffic (GSM or UMTS) can be relayed cost effectively between the SCs and the BSs by exploiting the benefits of SMF technology.

It involves the remoting of antennas to suitable locations at satellite earth stations.By so doing, high requency equipment can be centralised.The second application involves the remoting of earth stations themselves.

  • Mobile Broadband Services

The Mobile Broadband System or Service (MBS) concept is intended to extend the services available in fixed Broadband Integrated Services Digital Network (B-ISDN) to mobile users of all kinds. Since very high bit ates of about 155 Mbps per user must be supported, carrier frequencies are pushed into mm-waves.Therefore, frequency bands in the 60 GHz band have been allocated.

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