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Optical Coherent Detection and Processing Systems
Published in Le Nguyen Binh, Advanced Digital, 2017
A typical schematic diagram of a coherent optical communication employing a guided wave medium and components is shown in Figure 5.1, in which a narrow band laser incorporating an optical isolator cascaded with an external modulator is usually the optical transmitter. Information is fed via a microwave power amplifier to an integrated optic modulator, usually the LiNbO3 or EA types. Coherent detection is a principal feature of coherent optical communications, which can be further divided into heterodyne and homodyne techniques depending whether or not there is a difference between the frequencies of the LO and that of the carrier of the signals. A LO is a laser source whose frequency can be tuned and is approximately equivalent to a monochromatic source; a polarization controller would also be used to match its polarization with that of the information-bearing carrier. The LO and the transmitted signal are mixed via a polarization maintaining coupler and then detected by a coherent optical receiver. Most previous coherent detection schemes are implemented in a mixture of photonic and electronic/microwave domains.
Performance analysis of a multichannel WDM hybrid optical communication system for long haul communication
Published in Khaled Habib, Elfed Lewis, Frontier Research and Innovation in Optoelectronics Technology and Industry, 2018
D. Shanmuga Sundar, V. Nidhyavijay, T. Sridarshini, A. Sivanantha Raja
Optical communication is a form of telecommunication that uses light and optical fiber as carrier. In last two decades the fiber optic communication has seen a unique growth and technological evolution. Being developed in 1970s, the fiber optic communication system has revolutionized the telecommunication industry and has played a major role in the dawn of the Information Age. Due to the proficient consumption of power and low bit error rate, modified duo-binary return-to-zero (MDRZ) is special for the transmitter part of the system (B. Patnaik et al. 2012), (AnuSheetal et al. 2010). In the direction of exterminating pulse broadening, Optical Phase Conjugation (OPC) is taken into consideration which utilizes Four Wave Mixing (FWM) (C. Lorattanasane et al. 2009).
Introductory Concept
Published in Partha Pratim Sahu, Fundamentals of Optical Networks and Components, 2020
So Lmax depends more heavily on the constant αthan on the optical power launched by the transmitter. Figure 1.7 shows that the lowest attenuation is 0.2 dB/km at approximately wavelength region 1.5–1.6 μm. In optical communication system, the normal distance of optical propagation is 80 km without amplification. Using low loss fibers, amplifier spacing is enhanced from 80 to 160 km. The basic attenuations in a fiber are material absorption, scattering, bending losses and radiative losses of optical energy. The scattering loss is associated with structural imperfection and non-uniformity of fiber material composition. Radiative effects in fiber are due to fiber geometry which is bending (microscopic and macroscopic).
Distributed fiber optics sensors for civil engineering infrastructure sensing
Published in Journal of Structural Integrity and Maintenance, 2018
Among many emerging sensing technologies, Distributed Fiber Optic Sensing (DFOS) is one of the promising tools for structure health monitoring (Bao & Chen, 2011). In fact, the invention of optical fiber is one of the greatest technological achievements of the twentieth century. The concept of transmitting light waves over very long distance using optical fiber was developed by Nobel laureate Charles Kao in the 1960s and Corning glass laboratories produced optical fibers to realize this concept in the 1970s. Coupled with laser technology, optical fiber is one of the key components for the optical communication revolution.
Omnidirectional cylindrical graphene-based Bragg fiber in terahertz
Published in Waves in Random and Complex Media, 2021
Optical fibers find wide usage in optical communications and are used instead of metal wires due to the less loss and the immunity to electromagnetic interference. Optical fibers also have various other applications, such as fiber optic sensors and fiber lasers [1,2]. Optical fibers that typically include a high refractive index core surrounded with a low refractive index clad keep the light using total internal reflection phenomenon and act as waveguides [3]. Recently, photonic crystal fibers (PCFs) have attracted much attention due to their ability to confine light even in low-index or hollow-cores and confinement characteristics not possible in conventional optical fibers [4–7]. Potential advantages of hollow-core fibers are lower absorption loss and higher threshold power for nonlinear effects. The PCFs were first explored in 1996 and are now finding many applications. The PCFs may classify into two main classes: PCFs with a two-dimensional transverse periodicity [8] and Bragg fibers constructed from one-dimensional periodic concentric cylindrical shells [9–11]. The idea of using Bragg reflections in cylindrical waveguides was introduced in [12], and the first Bragg fibers were produced in 2000 [13]. Recently, researchers have paid much attention to the propagation of electromagnetic waves in a cylindrical photonic crystal (CPC) structure due to advances in modern manufacturing technology and the possibility of developing photonic crystals in different geometrical structures [14,15]. As one knows, the electromagnetic waves with arbitrary propagation wave vectors ) are not separable into the transverse electric and magnetic modes in the cylindrical geometry. However, in the absence of the z-component of the propagation wave vector, it is possible to separate the electromagnetic waves into the transverse electric and transverse magnetic modes. For this reason, in most articles, the propagation of electromagnetic waves in cylindrical geometry has been studied when the propagation wave vector does not have any component along the symmetry axis of the cylindrical structure [16–19].