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Introduction to Optical Networks
Published in Bijoy Chand Chatterjee, Eiji Oki, Elastic Optical Networks: Fundamentals, Design, Control, and Management, 2020
Bijoy Chand Chatterjee, Eiji Oki
WDM systems are categorized mainly into two different wavelength patterns, which are coarse wavelength division multiplexing (CWDM) and dense wavelength division multiplexing (DWDM). Coarse WDM systems typically use the band from 1.271 micron to 1.611 micron and support up to 17 channels, when 20 nm spacing is used. If Dense WDM (DWDM) systems use the C-Band (1.530 micron to 1.565 micron) transmission window with 100 GHz spacing, approximate 40 channels can be obtained; approximate, 80 channels can be achieved when 50 GHz spacing is used. The spacing between two wavelengths, denoted by Δλ, is estimated by (1.2) ()Δλ=λ02c⋅Δf,
Optical transmitters and receivers
Published in Matthew N. O. Sadiku, Optical and Wireless Communications, 2018
The role of the multiplexer is to transmit two or more channels simultaneously over the same fiber. The two popular multiplexing schemes used in fiber optics are time-division multiplexing (TDM) and wavelength-division multiplexing (WDM). TDM is the process of combining many channels of information within a single transmission channel by assigning each channel a different time slot. TDM is rarely used in fiber optics; it is more common in telephone (voice) systems. WDM is a scheme that combines several channels into a single fiber by assigning each channel a different wavelength. WDM is specific to fiber optics. As shown in Figure 2.7, several optical sources are transmitted at different wavelengths. The various wavelengths are injected into a single optical fiber. The light is filtered into separate wavelengths and converted to their respective electrical signals by the receiver.
Optical Fiber Hydrophone Systems
Published in Shizhuo Yin, Paul B. Ruffin, Francis T. S. Yu, Fiber Optic Sensors, 2017
Figure 9.14 shows the use of lumped EDFAs in a TDM–WDM hydrophone array. Here WDM sensor subarrays are multiplexed in TDM series. If WDM is multiplexing with N wavelengths and TDM multiplexing with M time slots, the total number of signal channels will be N × M. Previously, Kersey et al. [15] demonstrated a 64-channel TDM sensor array with EDFA. With the rapid development of WDM technology in recent years, the number of WDM wavelengths can now readily reach 32 or more. Hence, it seems that fiber hydrophone arrays could be constructed with a large channel count using both TDM and WDM techniques. A variation of interferometer configurations and interrogation schemes may be incorporated into a similar type of system arrangement. As an example, the figure shows a TDM–WDM based on the DDH scheme. The lights from different wavelength sources are converted into pulse trains, and then they enter a structure that produces frequency-shifted and time-delayed (twin) pulse trains.
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
The optical emission spectrum of the combined 18-channel CWDM signal is shown in Figure 7 for a 5G signal transmitted at a data rate of 20 Gb/s. The CWDM offers a favorable approach of delivering 20 Gb/s to the access network. The WDM-MUX is powered into the bidirectional SMF link of 210 km. WDM multiplies fiber capacity by multiplexing optical light signals of different wavelengths onto the SMF; the wavelength range of the fiber from 1271 to 1611 nm carries the baseband (digital signal) and analog signal (5G RF). The power level at the wavelength of 1271 nm to 1382 nm is in the region of −33 dB and from 1550 nm to 1622 nm is in the region of −12 dB. The wavelength of the 5G-RF signal is 1552.5. The green shaded area in the spectrum displayed in Figure 7 represents noise, which is due to the wireless RF signal and the laser diode. The spectrum confirms the dependency of the energy level on the wavelength.
Investigation of a coherent dual-polarized 16-QAM 16-channel WDM FSO gamma–gamma fading system under various atmospheric losses
Published in Journal of Modern Optics, 2022
With Wavelength division multiplexing (WDM) based FSO systems, we can overcome fibre optic communication's challenges for transmitting information signals over common channels [18]. Furthermore, an increase in channel count and a reduction in channel spacing can enhance data capacity. Wavelength division multiplexing (WDM) allows for better utilization of an optical fibre's transmission capacity. An optical multiplexer combines multiple wavelengths on a single optical channel, and a de-multiplexer separates multiple signals into separate optical wavelengths at the receiving end. Optical channels in the wavelength domain can be packed relatively closely together to determine the ultimate capacity of a WDM fibre network. The optical channels in dense WDM (DWDM) applications are closely spaced.
Traffic Grooming in PCE-based Architecture Combined with RWA Utilizing Dynamic Fiber State Information
Published in IETE Technical Review, 2018
Optical networks employing pure optical regeneration provide high data rates/speeds in the backbone network [1]. Wavelength division multiplexing (WDM) technique employed with optical amplifiers could multiplex a high number of wavelengths (or communication channels) on a single strand of fiber. Coarse/dense wavelength division multiplexing (C/D WDM) technology is driving backbone pure optical networks of the future, and providing these networks with data rates in the range of thousands of Gb/s in a single strand of fiber. Due to exponential increase of telecommunication, cellular, and internet user base around the world [2], this bandwidth will soon seem meager in comparison to backbone data rate requirements of the future. Traffic grooming is a process of combining various flows of data into a single channel thus optimizing existing bandwidth. Furthermore, traffic grooming can prioritize the flow of data as per various classes of service (CoS). Hence, an efficient traffic grooming algorithm (TGA) needs to be formulated to enhance the bandwidth utilization of these future telecommunication networks.