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Introduction
Published in Ke Wang, Indoor Infrared Optical Wireless Communications, 2019
The OWC principle has been proposed and developed to provide high-speed wireless connections in personal and LANs. One such example is shown in Figure 1.7. A broadband access network is deployed and high-speed connection is delivered to the “doorstep” of users’ premises, where an optical line terminal (OLT) provides broadband connectivity to users using the PON access technology. Inside the building, multimode fiber (MMF) or plastic optical fiber (POF) is used to provide high-speed wired connection, due to the easy coupling and the “plug-and-play” advantages. In addition to the wired communication, the OWC system is deployed to cope with the increased demand of wireless connectivity in such indoor environments.
Optical network architectures
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
The ONUs are usually positioned at different distances from the local exchange. Therefore, the upstream transmission of the packets from each ONU should be carefully timed, in such a way that the packets do not collide at the network splitter [11,14]. The OLT has to measure the distance to each ONU for this, and then instructs the ONU to insert an equalizing transmission delay such that all distances from the ONUs to the OLT are virtually equal to the longest allowable distance (i.e., 20 km); see Figure 2.28. To measure the distance to each ONU, the OLT emits a ranging grant to each ONU, and on receipt the ONU returns a ranging cell to the OLT. In this distance ranging process, the OLT can deduce the distance to each ONU from the round trip delay.
Green Hybrid Wireless-Optical Broadband Networks
Published in Gurjit Kaur, Akanksha Srivastava, Green Communication Technologies for Future Networks, 2023
In this network, the PON technique is most widely used, which offers significant utilization of the bandwidth of optical fiber with high data rate. The main parts of the PON architecture are an optical line terminal (OLT) that resides at the center office (CO) and ONUs. The traffic routes from OLT to ONU in a downstream way, while it is in upstream direction when the traffic routes from ONU to OLT. Based upon the multiplexing techniques, PON is subdivided into three types: time division multiplexing PON (TDM-PON), wavelength division multiplexing PON (WDM-PON), orthogonal frequency division multiplexing PON (OFDM-PON), and hybrid PONs.
5G Mobile Wireless Access and Digital Channeling with RF Over Fiber for Long-Haul 64-QAM Communication
Published in IETE Journal of Research, 2023
Mazin Al Noor, Bal S. Virdee, Karim Ouazzane, Dion Mariyanayagam, Harry Benetatos, Svetla Hubenova
Successful transmission is demonstrated for 5G 64-QAM OFDM channels via combined GPON and RFoF architecture. Here the 5G 64-QAM channels are fed into the OLT’s Mach–Zehnder modulator. The continuous wave (CW) laser-diode used delivers an output power of 3 dBm at a frequency of 193.1 THz, with a linewidth of 10 MHz, relative noise-dynamic range of 3 dB, and noise-threshold of −100 dB. Laser-diode CW radiates a light wave of frequency 193.1 THz into MZM to modulate with 5G. The resulting optical wave is launched into the fiber and fed into WDM-MUX. WDM assures signal integrity for various RF signal formats and prevents interference with the GPON-CWDM spectrum. Emission wavelengths from the laser were set with a 20 nm pitch CWDM grid to operate with the base station. The 18-channel CWDM wavelength is launched into WDM-MUX, which combines it with a 5G signal into a single bidirectional SMF of length 160 km connected at the end to a bidirectional splitter. The splitter separates the optical signal to multiple fibers and distributes the downstream data (20 Gb/s) from/to the OLT and WDM-DEMUX. The signal is then combined with the upstream data (10 Gb/s) from ONUs and WDM-DEMUX to a single OLT.