Optical fiber is the medium of strange for high capacity digital transmission systems and high cartoon local place network. Besides these applications, optical fiber moreover can be used to transmit microwave signals for cable television, cellular radio, WLAN and microwave antenna remoting. To transmit microwave on height of optical fiber, the microwave signal is converted into optical form at the input of the fiber and at the output of the fiber, it is converted charity to electrical signal. The main advantage of fiber transmission of microwave is shortened losses relative to metallic media (e.g. copper coaxial cable). This results in longer transmission set against without signal amplification or use of repeaters.
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There are two approaches to optical signal modulation and recovery. The first type is IMDD (Intensity Modulation Direct Detection) and the second type is Coherent Detection. In IMDD, the optical source severity is modulated by the microwave signal and the resulting severity modulated signal passes through the optical fiber to a photodiode where the modulation microwave signal is converted protection to electrical domain. In Coherent Detection, the optical source is modulated in extremity, frequency or phase by the microwave signal. The modulated signal passes through the optical fiber to the receiver where it is impure as soon as the output of a local oscillator (LO) laser. The cumulative signal is converted to electrical domain using a photodiode. This produces an electrical signal centered behind reference to the difference frequency along amid the optical source and the LO laser (i.e. intermediate frequency). This signal is adjunct processed to recover the analog microwave signal.
RFoG (Radio Frequency on pinnacle of Glass) is the cable operators’ implementation of microwave transmission cutting edge than optical fiber in which the coax portion of the HFC (Hybrid Fiber Coax) is replaced by a single fiber, passive optical network architecture (PON). RFoG allows cable operators to deploy fiber connectivity to customer premises (FTTP) even though keeping its existing HFC and DOCSIS infrastructure. Like the HFC architecture, video controllers and data networking facilities are fed through a CMTS/edge router.
These electrical signals are along with converted to optical and transported via a 1550 nm wavelength through a wavelength detachment multiplexer (WDM) and a passive splitter to a R-ONU (RFoG Optical Network Unit) located at the customer premises. R-ONUs postpone the fiber connection and convert the traffic to RF for delivery greater than the in-blazing network. Video traffic can be fed on zenith of coax to a set-elevation crate, even though voice and data traffic can be delivered to an embedded multimedia terminal adapter (eMTA), The reward passage for voice, data, and video traffic is in help-thinking than a 1310 nm or 1590 nm wavelength to a recompense passage receiver, which converts the optical signal to RF and feeds it back into the CMTS and video controller.
The advantage of radio-on summit of-fiber technology is that it centralizes most of the transceiver functionality by transmitting the microwave signals in their modulated format anew fiber. This reduces the number of right of entry points to antennas as well as amplifiers and frequency converters. In-building passive picocell for GSM or UMTS is implemented using radio-along along in the midst of more-fiber. Wireless base stations are located in a central communications room and their outputs/inputs fed through RF multiplexers to lasers/photodiodes contained within the optical transceiver hub. The modulated optical signals are related to/from the detached antenna units (AUs) in the building using single-mode optical fiber. The base station uses a entire quantity detector/optical modulator, which is directly coupled to the antenna, in view of that that no electrical amplification or new government is required.