Query: mode divison multiplexing

title: Mode divison multiplexing over few mode fibers
abstract: We report about mode multiplexed transmission over few mode fibers with 10 or more spatial modes. We also describe the latest progress in mode multiplexers and optical amplifiers.

title: Performance of Dual mode OFDM IM using Reduced Complexity Receiving Technique
abstract: Dual Mode Index modulated Orthogonal Frequency Divison Multiplexing is a technique, which eliminates the spectral efficiency limitations of standard index modulated Orthogonal Frequency Divison Multiplexing. This dual mode technique improves spectral efficiency by using all subcarriers for information transmission. The subcarriers are divided into several smaller sub blocks. There are two groups of subcarriers in every sub block based on index bits, known as active subcarriers and inactive subcarriers. The active subcarriers are modulated by primary signal constellation and inactive subcarriers are modulated by a secondary signal constellation. The information carrying bits include, bits corresponding to classic signal constellation symbols which actually travel through the wireles channel and also the index bits that are used for indexing the active subcarriers. In this paper we have analysed the BER performance of the above modulation technique for different system parameters with the aim of having an energy efficienct as well as spectrally efficient signalling scheme with a simple receiving technique.

title: Tapered Fibers Technology for Multi functional Neural Interfaces
abstract: We exploit mode divison multiplexing and demultiplexing in tapered optical fibers to optically interface with the brain, enabling depth resolution in sub cortical structures with only one and minimally invasive waveguide.

title: Novel fiber optic geometries for fast quantum communication
abstract: Recent experiments have generated great interest in combined wavlength (WDM) and spatial (SDM) divison multiplexing using optical angular momentum (OAM) at data rates orders of magnitude better than current telecommunication standards. We discuss here a class of novel fiber optic devices that induce mode coupling along the optical axis of the fiber by sinusoidally varying the refractive index. Using the analogy between the wave equation for weakly guiding fibers and the paraxial equation, we review fibers that support Laguerre Gauss modes and, motivated by these works, demonstrate that similar fibers with different core shapes support Hermite Gauss modes in the same regime. Finally, we utilize these relations to demonstrate how one might generate different orbital angular momentum states using induced coupling between Hermite Gauss modes, motivated by the works of many previous authors. We further describe a class of devices that could generate either a mode with a defined orbital angular momentum, and support its propagation along a fiber, or create a superposition of modes from a single modal input. Previous efforts focused on the generation of OAM states in a fiber have required extremely exotic refractive index profiles, and we present here a method based on already developed refrative index profiles and manipulation techniques, specifically using fiber bragg gratings to drive modal coupling in a fiber, in an effort to generate states with well defined OAM.

title: Reliability test procedures for tunable lasers
abstract: Widely tunable lasers are promising sources for future high capacity dense wavelength divison multiplexing and photonic switching systems. These devices can be used for sparing in the cold standby mode, restoring in hot standby restoring, rerouting wavelength rerouting or conversion, or fast switching in all optical networks. Tunable lasers need to demonstrate some featuers such as wide tunability range, optical output power of 10 dBm or more, cost and structure similar to those of commercial DFB lasers. High performance devices would require low laser chirp, high modulation speed, small size and very high reliability. For system applications, requirements on the tunable laser reliability are very stringent. Reliability studies and appropriate related testing procedures are necessary to define stability of tunable lasers and their expected lifetime. In this paper we propose some reliabilty test 'strategies' useful for qualification of tunable lasers with reference to some critical issues of the main technologies used to achieve the tunability feature.

title: Theoretical Study for Wavelength Conversion of Cascaded Second Order Nonlinearity in Silica Fiber
abstract: In this paper, A novel wavelength divison multiplexing (WDM) nets is proposed by use of cascaded second order nonlinearities (kh(2):kh(2) in the D fiber grating after periodically thermal/electric field poling, and is theoretically analyzed for the first time. The coupled mode equations of the kh(2):kh(2) nonlinearities are derived, and the analytic expressions for the electric field amplitude of converted light wave and the conversion efficiency e are obtained under the small signal approximation, which are well consistent with numerical calculations. Both analytic expressions and numerical results show that, under the phase matching, e is proportional to the logarithm of the square of pump light power, and the 4th power of the grating length L and the second order nonlinearity d. The calculated results also show that e and Dl of this fiber grating can be reached over 17dB and 120nm, respectively. With the increase of L, e increases rapidly while Dl decreases quickly. The results of simulated calculations and theoretical analysis show that the cascaded kh(2):kh(2) process is different from quasi phases matched difference frequency generation.

title: Studies of Some Problems in Optical Soliton Communications
abstract: Optical soliton communication is expected to be one of the most promising candidates for ultralong distance and extremely high bit rate communications.In this dissertation,we study some important problems in optical soliton communications.This dissertation consists of three sections.Section 1 is the study of soliton propagation in birefringent fibers.Section 2 is the study of single channel optical soliton communication systems.Section 3 is the study of wavelength divison multiplexing(WDM) optical soliton communication systems.The main contents of this dissertion are as follows:(1) A generalized nonlinear coupled mode equation to describe the ultrashort pulse propagation in optical fiber with arbitrary modes present is proposed.Starting with these coupled equations,the nonlinear propagation equations with fundamental solitons orthogonally polarized in birefringent fiber are obtained naturally.(2) The collison of orthogonally polarized fundamental silitons in birefgingent fibers is investigated numerically.The effect of the initial separation of the two solitons on the soliton collisions is discussed.(3) The fact that the impact of Ramam effect on ultrashort orthogonally polarized soliton interacts in birefringent fibvers is studied.The Ramam gain and Ramam frequency shift is analyzed.(4) The effect of random birefringence on the stability of long distance soliton propagation is investigated numerically.The empiric formula to avoid the effect of random birefringence is given.(5) We find that positive initial chirp increases the time shift of the soliton in soliton dragging logic gate.and the negative initial chirp decreases the time shift.(6) The dynamic soliton communication and path averaged soliton communication are compared by using numerical simulation.(7) The effects of the nonideal gain of EDFAs on path averaged soliton propagation in long fibers are studied.(8) The exact expression of the bit error rate for optical soliton communication systems with lumped amplifiers in proposed in consideration of the com

title: Design and experimental demonstration of a silicon multi dimensional (de)multiplexer for wavelength mode and polarization division (de)multiplexing.
abstract: Leveraging the physical dimensions of an optical carrier (e.g. wavelength, mode, or polarization) allows significant scaling of the transmission capacity for optical communications. Here we propose a scheme for implementing on chip silicon (de)multiplexers with simultaneous wavelength mode and polarization division (de)multiplexing capability. The device is constructed by using cascaded subwavelength grating (SWG) based contra directional couplers. To verify the feasibility of the proposed structure, we perform a proof of concept experiment of an 8 channel (de)multiplexer with two wavelengths, two modes, and two polarizations. The insertion losses are lower than 6.6 dB and the crosstalk values are below 18.7dB at around 1540 nm and 1550 nm for all the eight channels.

title: Communicating Using Spatial Mode Multiplexing: Potentials, Challenges, and Perspectives
abstract: Time, polarization, and wavelength multiplexing schemes have been used to satisfy the growing need of transmission capacity. Using space as a new dimension for communication systems has been recently suggested as a versatile technique to address future bandwidth issues. We review the potentials of harnessing the space as an additional degree of freedom for communication applications including free space optics, optical fiber installation, underwater wireless optical links, on chip interconnects, data center indoor connections, radio frequency, and acoustic communications. We focus on the orbital angular momentum (OAM) modes and equally identify the challenges related to each of the applications of spatial modes and the particular OAM modes in communication. We further discuss the perspectives of this emerging technology. Finally, we provide the open research directions and discuss the practical deployment of OAM communication links for different applications.

title: Space division multiplexing in standard multi mode optical fibers based on speckle pattern classification
abstract: In optical communications the transmission bandwidth of single mode optical fibers is almost fully exploited. To further increase the capacity of a telecommunication link, multiplexing techniques can be applied across 5 physical dimensions: amplitude, quadrature, polarization, frequency and space, with all but the latter being nearly exhausted. We experimentally demonstrate the feasibility of an original space division multiplexing technique based on the classification of speckle patterns measured at the fiber's output. By coupling multiple optical signals into a standard multimode optical fiber, speckle patterns arise at the fiber's end facet. This is due to quasi random interference between the excited modes of propagation. We show how these patterns depend on the parameters of the optical signal beams and the fiber length. Classification of the speckle patterns allows the detection of the independent signals: we can detect the state (i.e. on or off of different beams that are multiplexed in the fiber. Our results show that the proposed space division multiplexing on standard multimode fibers is robust to mode mixing and polarization scrambling effects.