Fiber Optic Communication Links

The development of optical communications systems from long fibers to compact wireless networks has led to the possibility of linking two satellites using a wireless optical link. The optical communication systems have been upgraded to use of wireless systems. The two satellites can be connected using optical wireless link. The optical wireless communication allows the exchange of information between two satellites at a higher speed. To act as a source of light, laser can be used and as an optical link, and a high-frequency light signal can be used. In this paper, we are analyzing and optimizing the different aspects of an optical communication link by selecting different modulation scheme. The IS-OWC link has been analyzed using PSK, DPSK, and OQPSK. The bit error rate (BER) and Q-factor have been used as the main determinant to analyze the performance of optical link between two satellites.

We develop a new model to describe the Mode Partition Noise (MPN) in VCSEL-Based Multi-Mode Fiber (MMF) links starting from the well-known Langevin noise-driven laser rate equations. Using the spatio-temporal representation of the rate equations for the VCSEL transverse modes, we develop a comprehensive physical model for VCSEL noise properties using covariance (COV) matrix approach. Neglecting second-order effects, we then reduce the COV matrix elements to three VCSEL-specific parameters ${{\alpha }}$ , ${k_n}$ and ${{\Gamma} _{\boldsymbol p}}$ , which completely characterizes the VCSEL noise. We further illustrate that the VCSEL Relative Intensity Noise (RIN) influences the MPN penalty and thus cannot be treated independently. The model also describes the dependence of the VCSEL mode correlation properties on the relative time-delays which can be measured as fiber-enhanced RIN. Lastly, we verify experimentally the new model assumptions about the cross-correlation properties of the VCSEL modes through direct experimental measurements on 900 nm VCSELs of known RIN which shows that the cross-correlation coefficient ${{\boldsymbol{R}}_{{\rm{ij}}}}$ is different for different mode pairs with a positive ${{\boldsymbol{R}}_{{\rm{ij}}}}$ between 1 and 3 modes. This validates the new model predictions, while contradicting the O–A model assumptions when applied for VCSEL-based links.

Low computationally complex recurrent neural network for high speed optical fiber transmission

Disruption-tolerant networks (DTNs) are groups of network assets connected with a suite of communication protocol technologies designed to mitigate the effects of link delay and disruption. Application of DTN protocols to diverse groups of network resources in multiple sub-networks results in an overlay network-of-networks with autonomous data routing capability. In space environments where delay or disruption is expected, performance of this type of architecture (such as an interplanetary internet) can increase with the inclusion of new communications mediums and techniques. Space-based optical communication links are therefore an excellent building block of space DTN architectures. When compared to traditional radio frequency (RF) communications, optical systems can provide extremely power-efficient and high bandwidth links bridging sub-networks. Because optical links are more susceptible to link disruption and experience the same light-speed delays as RF, optical-enabled DTN architectures can lessen potential drawbacks and maintain the benefits of autonomous optical communications over deep space distances. These environment-driven expectations - link delay and interruption, along with asymmetric data rates - are the purpose of the proof-of-concept experiment outlined herein. In recognizing the potential of these two technologies, we report an initial experiment and characterization of the performance of a DTN-enabled space optical link. The experiment design employs a point-to-point free-space optical link configured to have asymmetric bandwidth. This link connects two networked systems running a DTN protocol implementation designed and written at JPL for use on spacecraft, and further configured for higher bandwidth performance. Comparing baseline data transmission metrics with and without periodic optical link interruptions, the experiment confirmed the DTN protocols' ability to handle real-world unexpected link outages while maintaining capability of reliably delivering data at relatively high rates. Finally, performance characterizations from this data suggest performance optimizations to configuration and protocols for future optical-specific DTN space link scenarios.

Introduction In the preceding chapters we discussed the characteristics of optical fibers, optical sources, and optical detectors. These form the three basic units of any optical fiber communication system. In this chapter we discuss how these basic elements can be put together to build a simple point-to-point optical fiber communication link. Let us assume that we need to transmit information between two points (see Figure 13.1). The separation between these points could range anywhere from less than a kilometer in the case of computer data links to several thousands of kilometers, for instance, in transoceanic links. In all such links, there would be a transmitter that could be either an LED or a laser diode, the transmission path consisting of optical fibers that could be either multimode or singlemode fibers, and the optical receiver that could be a PIN or APD followed by the detection electronics. The choice of the components would depend on the distance as well as on the bit rate. When the separation between the points is greater than about 50–100 km, then because of attenuation in the link or pulse dispersion, it becomes necessary to use regenerators that consist of a receiver–transmitter combination. These regenerators detect the pulse stream before the power becomes too low or the pulses become unresolvable and retime, reshape, and regenerate (and, hence, the name 3R repeater) a new set of optical pulses to be transmitted over the next part of the link. For links that are limited by loss rather than by dispersion, one can use optical amplifiers in place of regenerators.

The objective of this chapter is to define and analyze the key elements in the design of future ultra-high-speed relay systems based on optical technologies. Chapter Contents: 12.1 Introduction 12.2 Relevant missions and demos 12.3 System architectures 12.4 Optical channel model 12.4.1 Atmospheric channel 12.4.2 Pointing errors and microvibrations 12.4.3 Light coupling efficiency 12.5 Noise model 12.6 Link budget 12.7 Forward error correction 12.7.1 Full decoding on board of the relay 12.7.2 Decoding on ground only 12.7.3 Partial decoding scheme 12.7.4 Layered coding scheme 12.7.5 Interleaving options 12.7.5.1 Long PHY interleaver 12.7.5.2 PKT code with interleaved code symbols (packets) 12.7.6 Comparison of coding schemes 12.8 Summary Abbreviations References Inspec keywords: optical fibre networks; relay networks (telecommunication) Other keywords: optical technologies; ultra-high-speed data relay systems Subjects: Optical fibre networks

A synthesizer-free 28-GHz millimeter wave (MMW) carrier is generated by using orthogonally polarized dual-wavelength vertical-cavity surface-emitting laser (VCSEL) as the frontend transmitter. After equalizing the dual modes with an extremely weak power as low as -26 dBm (2.5 μW) at TM-mode polarization, the dual-wavelength power extinction of only 5.4 dB is achieved for optimizing the remote-node optical heterodyne of 28-GHz MMW carrier with a peak power of -59.8 dBm before antenna propagation with remaining similar relative intensity noise (RIN) as compared to the free-running case. Moreover, the mode partition noise (MPN) is increased less than 2 dBc/Hz by TM-mode injection at -26 dBm, whereas the TE-mode control results in unchanged noise spectrum as same as that obtained in free-running case even if the master power is increased to -18 dBm.

The objective of this paper is to highlight recommendations made by fifteen experts from industry and State Departments of Transportation (DOT) regarding the design, implementation, operations, and maintenance of fiber optic communication links presently being used in their transportation management systems. This paper also brings forth the problems faced during the deployment of these systems. The procedure followed for this research was to review the specifications and design guidelines for various Federal Highway Administration (FHWA) projects which have implemented, or are in the process of implementing, fiber optic communication links for their traffic management systems. DOT officials and industry design consultants who were directly involved in the implementation of the FHWA projects were then interviewed on issues concerning system design, operations and management, bidding, and other institutional aspects. The result of these interviews is a set of recommendations ranging from increased use of the latest standards to suggestions for more efficient planning of the traffic management center. These problems and recommendations are presented in this paper. This paper thus offers valuable guidelines for the design and implementation of fiber optic communication systems for future IVHS and transportation management applications.

The optimised characteristics of a wavelength-locked Fabry-Perot laser diode (FP-LD) have been analysed and demonstrated experimentally using remote seeding continuous wave (CW) optical source at central office (CO). The important issues of mode partition noise (MPN) of an FP-LD and Rayleigh backscattering arising from the same wavelength bidirectional transmission are investigated. The Q factor, sidemode suppression ratio (SMSR), and power penalty of a wavelength-locked FP-LD against signal-to-backscattering-power ratio (SBR) were measured. They can be optimised for the SBR range between 22 dB and 31 dB. From the measurements, both the MPN and Rayleigh backscattering can be controlled well owing to remote seeding of an FP-LD and hence use feasibly a wavelength-locked FP-LD in a wavelength division multiplexing-passive optical network (WDM-PON) optical link.

Polarization division multiplexing has emerged as an efficient solution for providing high-capacity information transmission rates in optical fiber communication links. But the practical deployment of optical fiber cables is not feasible in many circumstances such as areas having rough terrains and low populated areas keeping in mind the cost-effectiveness. Thus, free-space optics (FSO) transmission provides an effective technological solution in these circumstances and is a viable technology for last-mile broadband access. But, the degradation of optical beam quality in FSO links due to fog environment is a great matter of concern since both the optical beam and the fog particles are similar in size. In this work, we have discussed the simulative modeling and numerical investigation of a 160 Gbps data rate FSO transmission enabled by dual-polarization-256 level-quadrature amplitude modulation (DP-256-QAM) signal under the influence of fog environment. For improving the transmission performance under fog environment, digital signal processing (DSP) algorithms are implemented at the receiver. For analyzing the DP-256-QAM-FSO transmission, bit-error rate (BER) and constellation of the received signals are evaluated. The transmission investigation results exhibit reliable 160 Gbps data transportation at 5.5 km for sunny weather and 730 m for heavy fog environment.

Optical couplers are used in wavelength division multiplexing (WDM) applications for combining and separating wavelength channels, tapping off power for monitoring purposes, or adding and dropping specific wavelengths at a particular point in an optical fiber communication link. Most optical couplers are passive devices in the sense that they do not need to be powered externally to perform their function on optical signals. Fundamentally, optical couplers connect three or more fibers to combine, split, or redirect light signals. The key optical coupler performance parameters include insertion loss, excess loss, and crosstalk between channels.

In this paper, a model for the master-slave DC Microgrid over a fiber optic link is proposed. The delay margin is calculated according to Lyapunov-Krasovskii functional using the LMI toolbox in Matlab with the binary iteration algorithm. The optical fiber link is implemented using optisystem simulator. The optical fiber link is set to transmit the digitalized reference current from master controller to the slave controller. The link tested at 100Mbps, 1Gbps and 2.5Gbps data rate values and several optical fiber lengths and wavelength of 1550nm and 1400nm. The results show that the performance of the link is sufficient at received power more than -30dBm for all data rate values at 1550nm. While at 1400nm, the attenuation rate is very high. Therefore, the link must be 10km to achieve acceptable performance. This wavelength is used in this simulation to avoid the C band and O band, which used for telecommunication purposes.

We present, for the first time, a study of polarization instability induced RIN (relative intensity noise) enhancement in VCSELs. Devices under study are nominally single-mode top-emitting GaAs/AlGaAs VCSELs with an operating wavelength of 850 nm. Current confinement and gain guiding are obtained by double proton implantation. Detailed results of bit error rate measurement on free-space optical links with polarization-unstable VCSELs and a rate-equation based model of the polarization instability are presented.

Active systems and raster scans are the most popular methods for achieving the pointing accuracy required to form an optical link. With advances in vision system technology, a potential extension to current methods of alignment is to use cameras to control coarse and/or fine pointing acquisition and tracking to establish covert optical communication links. The narrow beam width of an optical link requires very accurate pointing capabilities that are not achievable by low-resolution cameras. This paper focuses on analyzing the feasibility for a vision system to establish a covert optical link between two terminals.

The most effective solutions available now for information security and protection, industry development, digitization, and operation for future generations are fiber optic networks. In this connection, we used the Optical Reflectometer OTDR to analyze an actual optical link between Skikda-Elharrouche for two different wavelengths offered by "Algeria Telecom". Using the optical simulator OPTISYSTEM, the same network was constructed with the purpose of verifying the optical connection quality by virtual monitoring and cross-referencing with the actual data sheet. The two application wavelengths chosen for the experiment and test were 1310 nm and 1550 nm. By selecting suitable link parameters, we found that the line does not present major defects compared to the results of the OTDR (Optical Time Domain Reflectometer). By simulating the connection in the opposite direction using OptiSystem software, the settings were verified. Results of eye diagrams, the minimum BER (Bit Error Rate) value reaching 2.377 10-25 for 1550nm and 7.279 10-45, and quality factor which reaches the value of 10.327 at 1550nm, and the value 14.004 at 1310nm, showed that Skikda-Elharrouche optical link performed better comparing to OTDR results.