Papers by Keyword: Optical Fiber Communication

Abstract: A comprehensive theoretical model of direct detection (DD) optical orthogonal frequency division multiplexing (OOFDM) system is described in general. The principle of OOFDM is introduced in detail. Several key technologies in DD-OOFDM system have been discussed. The advantages and methods for optical single sideband (OSSB) and channel estimation are analyzed completely. Other key technologies are introduced briefly.

Abstract: The losses of the off-axis rotary optical fiber communication system were derived from optical fiber coupling, three kinds of misalignments between optical fiber collimators (Axial separation Z₀, lateral offset X₀, angular tilting θ), incomplete alignment of optical fiber collimator during rotation and system tremble caused by high speed rotating. Some measures were taken to reduce the loss. The thermally expanded core fiber collimator cut down the influence of axial separation and angular tilting. The position of the optical fiber collimator on the flange was adjusted and infrared right angle prisms were installed to reduce the losses during rotation of the system. In addition, improving the precision and optimizing device of mechanical structure can increase the stability of the whole experiment platform and decrease the losses.

Abstract: An optical 90^o hybrid consisting of a general interference based 4×4 MMI coupler, a phase shifter and a 2×2 MMI coupler was proposed. This device can demodulate optical signal without intersections. The output power formula of this device was derived from theory, and the effect on phase shifter was discussed analytically and numerically. It is not necessary to control phase shifter accurately, a deviation 10^o form perfect phase shift will introduce 2% AC component loss of Q information only.

Abstract: In this paper, a mode conversion model is proposed to increase the capacity of optical fiber communication systems. In this model, a spatial spectral matching method is used to convert the original mode to the desired mode for mode division multiplexing in optical fibers. A binary phase spatial light modulator is employed on the Fourier plane as a spatial filter. Numerical results show that the original modes can be converted to the desired modes.

Abstract: We demonstrate a system scheme of generating and transmitting base-band and radio frequency signal based on optical double-sidebands scheme to generate optical millimeter-wave signal via optical phase modulation (OPM) and FBG. The system architecture with the source of laser at central station, the data re-modulation on downlink optical carrier gained from one base station is a good method to reduce the cost of uplink transmitter, for it does not needs the source of laser and wavelength administration at the base station. The optical phase modulator is inexpensive and mature. The downlink communicated bandwidth can be doubled to realize Ultra Width Band & Ultra High Frequency (UHF) communication via phase modulation and FBG at the base station. And the other signal which is reflected by FBG can be reused as uplink via amplitude modulation availably. The simulation results show that the bi-directional 2.5Gbit/s data and UHF microwave with 24GHz is successfully transmitted over 50km distance of a single-mode optical fiber with a optical dispersion of 20ps/(nm·km), an optical attenuation of 0.25dB/km and a light source power of 3dBm.

Abstract: In order to realize the large capacity of ultra-high-speed optical fiber transmission, optical modulation and reuse is one of crucial technology. This article discusses MAMSK modulation format all-optical OOFDM transmission system. The MAMSK modulation format with the method of phase modulation combined with multiple amplitude modulation, at the same time on the signal phase and amplitude modulation information, achieve the goal of lower code rate. All-optical OOFDM multiplexing technology is the electric field of OFDM, half its adjacent subcarrier frequency spectrum overlap, so the spectrum efficiency is very high, is a kind of very potential recovery technology.

Abstract: We propose and develop a passive alignment technique of 4 output waveguides of PLC-based 90° OH and a 1×4 PD array. This alignment technique only uses an infrared CCD camera and an infrared light.

Abstract: For high bit-rate optical communications system, the changes in temperature or power fluctuations are due to the dispersion of the dispersion tolerance than the system. Therefore, the dispersion compensation unit must have the functionality to adapt to the dynamic generation of tunable optical communication network development. This article describes several dynamic tunable compensation techniques and the basic principles of the performance characteristics of the situation at home and abroad, including the chirped fiber grating method, the virtual image phased array method, GT interferometer method, the array method and the planar waveguide grating method, and a brief discussion of tunable dispersion compensation technology in the future direction of development.

Abstract: This paper presents the background of PON (Passive Optical Network), introduces the powerful communication design and simulating software which named Optisystem, show the PON(Passive Optical Network) theory and structure, designs the PON fiber link which has 1310nm uplink wavelength and 1490nm downlink wavelength and then analyses the models performance. In the software, we set up a rate of 1Gbps model of PON by using the component in the Optisystem. Through calculating the model, the document gets the spectrum figure of the simulate fiber link, and analyses the parameter, such as spectrum character, Q factor, eye diagram and BER, the result verified the validity and practicable of the models design, makes the result that the initial character fiber link cant meet the demand of optical communication, so changing the transmission distance to 10 km , transmitter power to-1dBm, meeting and obtaining the basic requirements of the system performance, after that the paper comparing the coding between none return to zero (NRZ) and return to zero (RZ) encoded mode, the eye diagram analyzer component show that NRZ code is better than RZ code, in the end of the paper there is the conclusion.

Abstract: To overcome the problem that the artificial scheduling can not deal with optical fiber switching in time when optical fiber is broken or damage in power system, we designed an optical fiber line auto switch protection system. The system used six 4x4 optical switches to compose an optical switch array that eight working fibers can share four alternate fibers. Comparing with other system, the new system more effectively utilizes alternate fibers, and is more suitable for practical power system. It used single chip microcomputer as control chip of optical switch, when the received optical power is lower than predefined threshold, the control chip will control the optical switch to alternate fiber line in time to ensure the real time and reliability of optical fiber communication. In the same time, the new system can communicate with host computer to alarm, display fault optical fiber line and remote control, and be controlled by button to realize the manual switch of optical fiber line.