Single-mode Optical Fiber Systems Research Articles

Multipoint Bending Measurement Using Multicore Fiber Bragg Grating and Two-Photon Absorption Process in Si-APD

We propose and demonstrate a fiber optic multi-point bending measurement system that uses Bragg gratings inscribed along a multi-core fiber (MCF) and a silicon avalanche photodiode (Si-APD) that produces two-photon absorption (TPA) photocurrent for 1.55- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> light. Because the TPA photocurrent from the Si-APD is proportional to the mean square of the optical intensity, the intensity correlation between 1.55- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> probe and reference beams is measured from it without using complex electrical circuits. The proposed system has different lengths of optical fibers between each core of MCF and input/output ends of a single mode fiber optic system, which makes different the correlation signal between the reference beam and the probe beam reflected from different Bragg gratings in MCF. That enables the reflection spectra of all the Bragg gratings in MCF to be separately measured even when they are overlapped in the wavelength domain. As a result, the bending radius and its direction are measured without using multiple detectors or optical switching devices. We conducted proof-of-concept experiments by using a 7-core MCF with almost the same Bragg gratings inscribed in each core at three points along the fiber. We also demonstrated an example of application to shape measurement.

The Electrical Engineer Who Clarified Glass [Scanning our Past

Charles Kuen Kao Life Fellow of the IEEE and Nobel Laureate, died from Alzheimer's disease on September 23, 2018 in CA, USA, after a rich life of work and family in the United Kingdom, the United States, and Hong Kong. The Nobel committee in physics honored him in 2009 “for groundbreaking achievements concerning the transmission of light in fibers for optical communication.” He spent his engineering career at the International Telephone & Telegraph Company's (ITT's) Standard Telecommunications Laboratories (STL) in and near London, where he organized and championed the development of single-mode fiber optic systems in the 1960s.

Failure Analysis of Fiber Optic Communication System in Deep-Water Remotely Operated Vehicle ROSUB 6000

AbstractSingle-mode fiber optic systems can play vital roles in cabled deep-water vehicle operations at greater depths (&gt;3,000 m). One kind of single-mode fiber optic system, the ROSUB 6000, is used in a deep-water work-class remotely operated vehicle (ROV). Fiber optic link failure of ROV telemetry and sound navigation and ranging were noticed at a water depth of 3,050 m during the ROSUB 6000 system sea trials. A failure analysis of the fiber optic communication system was carried out with the link data logged during different phases of the deep-sea trials. The results from the failure analysis carried out during deep-sea trials showed an increase in the fiber optic link loss from a depth of 900 m onwards. Further analysis of the fiber optic link loss in the laboratory involved pressure and low-temperature testing of all the subsea components in the ROV telemetry link. From the laboratory pressure test results, it was concluded that pressure was not the root cause of the fiber optic link failure. On further analysis, a complete fiber optic link failure was noticed during the low-temperature testing of the subsea components. Furthermore, the low-temperature testing of the individual subsea components revealed that the fiber optic rotary joint (FORJ) insertion loss increased rapidly at low temperatures. This FORJ insertion loss led to complete failure of the fiber optic links in the ROV. The degradation of index-matching fluid in the FORJ was identified to be the root cause of fiber link failure.

Numerical Simulation of Chromatic Dispersion and Fiber Attenuation in a Single-Mode Optical Fiber System

Chromatic dispersion and fiber attenuation pose a great problem in the detection of optical signals. Dispersion causes pulse broadening which limits the information carrying capacity of the fiber while attenuation limits the maximum transmission distance along the fiber. An approximate Gaussian pulse propagation model is obtained from the solution of Nonlinear Schrodinger Equation to represent the effects of chromatic dispersion and attenuation using Split-Step Fourier Method. It was found that pulse broadening and intensity loss in the optical signal is increasing proportionately with the propagation length of the fiber and this is what contributes to the causes of detection errors at the receiver. Keywords - Chromatic dispersion, fiber attenuation, intensity loss, optical signals, pulse broadening

Performance Comparison of LS and LMMSE Channel Estimation Algorithm for CO-OFDM System

The CO-OFDM single-mode optical fiber system is constructed by the Matlab coupled with the Optisystem. And the influence of different channel algorithm on the receiver of system is researched. The simulation results show that the system performance is improved by using LS or LMMSE channel algorithm. And the LMMSE channel algorithm can provide better performance than the LS channel algorithm. Compared with LS algorithm, the required receiver OSNR is reduced by about 1 dB using improved LMMSE algorithm at bit-error-rate (BER) =10-4 in the CO-OFDM single-mode optical fiber system.

Continuous-Wave Laser Stimulation of the Rat Prostate Cavernous Nerves Using a Compact and Inexpensive All Single Mode Optical Fiber System

Laser stimulation of the rat cavernous nerve (CN) recently has been demonstrated as an alternative to electrical stimulation for potential application in nerve mapping during nerve-sparing radical prostatectomy. Advantages include noncontact stimulation and improved spatial selectivity. Previous studies, however, have used large and/or expensive laser sources for stimulation. This study demonstrates the feasibility of optical stimulation of the rat CN, in vivo, using a compact, inexpensive all-single-mode fiberoptic system. A 1455-nm wavelength infrared diode laser beam was coupled into a 9-μm-core single-mode fiber for delivery through a 10F laparoscopic probe and used for laser stimulation of the CN in a total of eight rats, in vivo. Laser stimulation of the CN was observed at threshold temperatures of 41°C, with intracavernous pressure response times as short as 4 s, and magnitudes up to 50 mm Hg, compared with baselines of 10 mm Hg. This novel, all-single-mode-fiber laser nerve stimulation system introduces several advantages including: (1) lower cost laser; (2) more robust fiberoptic design, eliminating alignment and cleaning of bulk optical components; and (3) improved Gaussian spatial beam profile for simplified alignment of the laser beam with the nerve. With further development, laser nerve stimulation may be useful for identification and preservation of the CN during prostate cancer surgery.

The evolutionary potential of single-mode optical fibre systems

Single-mode optical fibre systems presently being installed in the BT network are primarily operating at 140 Mbit/s and 1.3 µm wavelength. There is scope for increasing the information capacity of these installed systems by both electrical and optical techniques. Three feasible upgrade options will be discussed and results of experiments performed at British Telecom Research Laboratories (BTRL) presented.

Analytical Description of Birefringence Statistics in Randomly Concatenated Single- mode Fiber Systems

Distributions on the Poincare sphere for the birefringence eigenpolarizations and the PMD vector in randomly concatenated singlemode optical fiber systems are analytically derived using Pauli's spin matrices for the description of birefringence. It is shown that both the distributions approach an uniform distribution on the sphere as the random concatenation increases. The convergence behavior is investigated using two different models by Wai and Menyuk for the local rectangular birefringence under inclusion of local circular birefringence. We find that, when the local birefringence is dominantly rectangular, the eigenpolarization approaches an uniform distribution (after ∼10 concatenated elements) much faster than the PMD vector ( ∼30 elements).

Gas detection based on optical correlation spectroscopy using a single light source

An alternative method of gas detection using optical correlation spectroscopy (OCS) has been investigated. A semiconductor optical amplifier (SOA) is employed to transmit broadband light through a reference and measurement cell containing the absorbing species, and the required 180° phase shift between the reference and measurement signal is achieved using an optical fibre delay line. The use of a single SOA light source reduces zero point drift errors that arise when two light sources are utilized and provides high compatibility with single mode optical fibre systems. A theoretical minimum detectable concentration of 0.15 ppm.m has been calculated and experimental results have been obtained for varying concentrations of acetylene (C2H2) gas at different pressures. The theoretical system response was determined using absorption data from the HITRAN database and compares well with the experimental results. Signal-to-noise ratio (SNR) analysis has been performed for our experimental system and an ideal system with minimal losses, an optimum filter and longer cell lengths.

Determination of Birefringence Configuration in Single-mode Fiber Systems through Backscattering Signal Analysis

We propose a method to analyze the evolution of the states of polarization measured by polarization optical time domain reflectometry. This method allows to obtain detailed information about the configuration of birefringence, which is present in the single-mode optical fiber system during the measurement. We include precise twist effects into the formalism. Long fiber systems can be modeled as concatenated wave plates, and the configuration is characterized by a data set corresponding to birefringence strength and eigenpolarization direction of these wave plates.

Analytical form of frequency dependence of dgd in concatenated single-mode fiber systems

An analytical form for the lightwave angular frequency (/spl omega/) dependence of the squared value of the differential group delay in concatenated single-mode optical fiber systems is introduced. We show that the dependence can be described by a combination of cosine functions of rotation angles and their sums and differences of the fiber pieces, which are located between the two end pieces of the concatenated system. Using the analytical expression, the /spl omega/ dependence of real fiber systems can be simulated, providing information about the birefringence configuration of the system. Comparison with experimental data taken on real systems yields good qualitative agreement even if only few concatenations are considered.

Optical fiber audio and video communication system using AOM and LED

This paper describes the construction and performance of the single-mode (SM) optical fiber communication system utilizing the acousto-optic modulator (AOM) technique for modulation of audio and video signals. An edge-emitting LED (ELED) at an optical wavelength of 1300 nm was used as a light source. The output frequency response for the direct (Oth) and diffracted (1st) beams from the AOM used together with the ELED were flat over the frequency range of 50 Hz to 6 MHz. The differential gain (DG) and differential phase (DP) of the video signal were less than 5%, and 5 degrees, respectively, and the signal-to-noise ratio (SNR) was approximately 56 dB.

A single-mode optical fiber attenuator for intercomparison of attenuation

This paper presents the results of the investigation for developing an attenuator to be used in an intercomparison of attenuation values in single-mode optical fiber systems. The attenuation measurements in single-mode systems have a polarization-dependence problem corresponding to the mode-dependence problem in the multimode fiber systems. Therefore, an attenuator in which a small polarizer is placed was developed in order to obtain polarization-independent characteristics. If this attenuator is used as a transfer standard for the measurement comparison, any reference condition on polarization will not be required. >

Aperiodic power exchange due to parametric frequency generation in multiplexed optical fibre systems

We theoretically investigate parametric frequency generation and nonlinear power exchange in optical frequency division (or wavelength division) multiplexed single-mode optical fibre systems. When the initial signal powers are sufficiently high the different waves will exchange power due to the four-wave mixing process. We show that even in the simplest case of two input signals the resulting power exchange may demonstrate chaotic behaviour.

Modal noise in single-mode fiber-optic systems with closely spaced splices

Abstract Modal noise can be a problem in single-mode fiber-optic systems when short lengths of fiber are spliced into the system. Previous analyses have dealt only with lengths greater than 1 m. With very short lengths (< < 1 m), noise is not a problem, but modal interference can still manifest itself in the form of a time-invariant attenuation. Modal interference must be considered in the design of components that utilize very short pieces of fiber.

Statistical design of long optical fiber systems

A design strategy is proposed to minimize the most likely overall system cost, that is, the sum of the equipment installation cost and the repair cost over the lifetime of the system. By choosing a repeater spacing larger than that dictated by a worst-case design, the possibility of system failure due to negative system margin is admitted. However, for a correctly chosen repeater spacing, the most likely cost of repairing these failures, when added to the reduced installation cost, is significantly less than the system cost of a worst-case design. This statistical design strategy is applied to a 565-Mb/s single-mode optical fiber system operating at 1.3 mu m. Several different failure modes which can occur in such an optical fiber system are identified, and the probability density function for each type of failure is calculated. It is shown that the design strategy leads to significant savings compared with worst-case design. For typical device parameters, a saving of about 30% in equipment installation and repair costs over the lifetime of the system is reported. >

4×4 all-fibre optical switching matrix

This letter describes the fabrication and performance of a 4×4 nonblocking optical switching matrix for use with single-mode optical fibre systems. The configuration adopted uses individual 2×2 all-fibre switching units interconnected by fusion splices to form a 4×4 nonblocking matrix with a mean path insertion loss of 2.3 dB and a channel isolation better than −15 dB when operating at a wavelength of 1300nm.

Recent developments in the production of narrowband position tuned interference filters for wavelength multiplexed optical fibre systems

The performance of position tuned multilayer interference filters for use in the 1250–1600 nm wavelength range is described and analysed. These new filters have an improved performance with a wider tuning range (> 250 nm) and reduced fwhm (<10 nm) compared with earlier samples. These devices could find application for single channel selection in wavelength multiplexed single-mode optical fibre systems.

Integrated Optical Circuit Engineering

Implementation of single-mode optical fiber systems depends largely on the availability of integrated optical components for such functions as switching, multiplexing, and modulation. The technology of integrated optics is maturing very rapidly, and its growth justifies the optimism that now exists in the optical community.

System Penalty Effects Caused by Spectral Variations and Chromatic Dispersion in Single-Mode Fiber-Optic Systems

Optical submarine systems are now being planned, and because of the need for high levels of confidence in such systems, all aspects that affect performance need detailed investigation. Of particular importance are penalties that may arise from spectral effects. A theoretical and practical examination has been made of the relationship between source spectrum and system performance in the presence of chromatic dispersion. Equipment is described which provides an automatic record of the power budget penalty resulting from spectral variations for all temperatures in the operating range. Significant differences are found, even between lasers of the same type. The nature of the corresponding spectral differences is studied, and evidence is presented to show that both random and regular variations exert appreciable effects.