Transmission of optical communication signals by distributed parametric amplification

For the first time, to the authors' knowledge, distributed parametric amplification (DPA), i.e., the use of a transmission fiber itself for parametric amplification of communication signals is proposed and demonstrated. To account for the inevitable fiber loss, solutions were derived for the distributed amplifier, with either one or two pumps: They are obtained in terms of confluent hypergeometric functions. Low-penalty DPA of a 10-Gb/s nonreturn-to-zero (NRZ) signal over a 75-km dispersion-shifted fiber (DSF), is demonstrated by using only 66.5 mW of pump power. Three adjacent channels have been simultaneously transmitted, with little penalty due to nonlinear crosstalk. It is experimentally verified that DPA requires less pump power than distributed Raman amplification (DRA), for similar power penalties.     

Simplified adaptively modulated optical OFDM modems using subcarrier modulation with added input/output reconfigurability

Three novel designs of adaptively modulated optical orthogonal frequency division multiplexing modems using subcarrier modulation (AMOOFDM-SCM) are proposed,for the first time,each of which requires a ...     

Zero-dispersion wavelength mapping in short single-mode optical fibers using parametric amplification

We demonstrate a novel convenient nondestructive method based on optical parametric amplification that allows retrieval of the zero-dispersion wavelength map along a short optical fiber span with a high-spatial resolution. The improved resolution relies on the high sensitivity to the local longitudinal dispersion fluctuations of the parametric high-gain spectrum.     

Integrated optical amplifier for fast phase modulated signals

The amplifier is based on the optical Kerr effect in waveguides with large third-order nonlinear susceptibility. The short response time of the Kerr effect gives the device an extremely large bandwidth, exceeding that of any laser amplifier. Also, for binary signals, the amplifier is shown to have a phase regenerative effect. Examples of signal and pump powers are given for polydiacetylene waveguides     

光纤参量放大技术及应用

光纤参量放大基于在技术上的优势,越来越引起研究人员的重视.文章介绍了光纤参量放大器的结构及近期的研究情况,概述了其在分立集总放大、波长透明转换、慢光的产生,归零码生成及光时分复用(OTDM)等方面的应用.     

飞秒光参量放大技术原理及应用

飞秒光参量放大技术是一种获得宽带飞秒脉冲的有效手段.首先介绍了飞秒光参量放大技术的基本原理,并通过数值模拟显示了群速度失配及位相失配对信号转换过程的影响.数值计算结果表明:群速度失配及位相失配会导致转换效率下降,群速度失配还会导致脉冲发生畸变.其次,综述了该技术在超短脉冲特别是周期量级脉冲产生方面的研究进展,并介绍了Baltuska等设计的可以产生3.9 fs脉冲的非共线光参量放大装置.其中,详细讨论了超连续白光注入源、泵浦光角色散以及晶体选择三方面内容.最后介绍了该技术在高能飞秒脉冲产生方面取得的最新研究进展.     

Investigation on bismuth-oxide photonic crystal fiber for optical parametric amplification

A hexagonal solid-core bismuth-oxide micro-structure fiber is developed to balance its dispersion and nonlinearity.This simulation and calculation results show that the bismuth-oxide photonic crystal fiber(Bi-PCF) has near zero dispersion around 1550 nm.Its dispersion slop in the communication wavelength range is also relatively flat.Moreover,both nonlinear coefficient and model field distribution are obtained.Compared with the experimental results by SiO2-PCF,it can be seen that the Bi-PCF shows excellent characteristics for the optical parametric amplification(OPA).     

Influence of pump parameters on two-pump optical parametric amplification

An analysis of two-pump optical parametric amplifiers is proposed in order to evidence strategies to project and develop flat two-pump fiber parametric amplifiers (2P-OPAs). Amplifier gain profile is evaluated through a model that takes into account the four-wave mixing process with pump depletion. Disturbing influence of degenerate three-wave mixing processes is separately addressed. Through the analysis, important 2P-OPA project guidelines are obtained. Theoretical forecasts are confirmed by experimental measurements on different 2P-OPAs, realized by changing power and spectral allocations of the two pumps, obtained by Raman amplification.     

光学差分参量放大布里渊时域分析优化研究

为了优化设计基于光学差分参量放大的布里渊光时域分析抽运的脉冲编码形式以及斯托克斯光与反斯托克斯光脉宽差,采用微扰法和小信号近似法,获得了探测光与斯托克斯光脉冲、反斯托克斯光脉冲在较小作用区域内的脉冲响应,对其性能进行了理论分析与数值验证。结果表明,相位斯托克斯光脉冲可有效压缩布里渊增益谱宽,提高布里渊信号信噪比;当斯托克斯光与反斯托克斯光传感脉冲脉宽差为8ns时,探测光布里渊增益最大。这一结果对进一步分析基于光学差分参量放大的布里渊光时域分析系统性能以及开展相关实验研究是有帮助的。     

Amplification of WDM signals in fiber-based optical parametric amplifiers

We demonstrate for the first time, experimentally, the performance of fiber-based optical parametric amplifiers in wavelength-division-multiplexed (WDM) applications. Both a 3 /spl times/ 10 Gb/s and a commercial 7 /spl times/ 2.5 Gb/s WDM system are investigated together with the parametric amplifier. Limitations due to pump depletion and four-wave mixing are quantified. Measurements showing the performance in terms of power penalty and gain versus input-output signal power are presented.     

Polarization modulated direct detection optical transmissionsystems

A novel polarization modulated direct detection (PM-DD) system suitable both for binary and multilevel transmission is presented. At the transmitter the optical field is polarization modulated by a standard modulator. The receiver is based on the estimation of the Stokes parameters of the received optical field by means of a direct-detection optical front end and baseband electrical processing. The Poincare sphere rotation induced by the fiber is compensated by means of a purely electronic algorithm and the decision is performed in the Stokes space. The system performance is evaluated by an analytical model when the only relevant noise source is the receiver thermal noise and when erbium-doped optical amplifiers introduce amplified spontaneous emission (ASE) noise. The system is completely compatible with a direct-detection-based optical network, and it is possible to implement efficient multilevel modulation formats     

WDM passive optical network with subcarrier transmission and baseband detection scheme for laser-free optical network units

We demonstrate a new scheme to achieve source-free optical network units (ONUs) in a wavelength-division-multiplexed passive optical network. The scheme utilizes subcarrier downlink transmission that enables penalty-free remodulation of the downstream signal for upstream transmission. The downstream data can be recovered at baseband either using an optical or electrical technique. In the optical scheme, the downstream signal is passed through a delay interferometer (DI) at the ONUs. A single variety of the DI is applicable to all ONUs that eliminates location-specific devices. Alternatively, the baseband data can be detected using a high-speed photodiode, a dc block, and a rectifier without any optical filter or phase locked loop for down-conversion. The upstream data is also detected at baseband without any modification to conventional receivers. We present experimental and simulation results for the scheme at 2-Gb/s downstream and upstream transmission over 20 km of fiber.     

The evolution of relative phase angle in optical parametric amplification

An alternate method is used to complement Baumgartner and Byer's analysis [1] of optical parametric amplification when all three waves are present initially. We emphasize the qualitative implications of the invariance of the product of the three amplitudes and the cosine of the relative phase angle for phase-matched wave propagation.     

Increasing acceptable number of signals in subcarrier multipleaccess optical networks in the presence of high optical beatinterference

This paper theoretically and experimentally demonstrates that our proposed method improves the carrier-to-noise ratio (CNR) of subcarriers and significantly increases the number of acceptable optical signals in subcarrier multiple access (SCMA) systems using distributed feedback laser diodes (DFB-LD's) with the same center optical frequency. This method reduces optical beat interference by using the multiplied product of the subcarriers and a low-frequency signal. From the experimental results using 1.3 μm DFB-LD's, the CNR sufficiently satisfies the required level even if the number of optical signals is three. Theoretically, the number of acceptable optical signals increases as LD's with wider optical line-width or with greater chirp coefficient are used. For example, assuming a laser chirp coefficient of 540 MHz/mA, the maximum number of LD's that can be used while still meeting the minimal CNR requirement is 12. This number corresponds to 66 optical beat interferences. Thus, this proposed beat-interference reduction technique is very effective in SCMA systems using DFB-LD's without optical frequency control     

MAP sequential detection of optical signals

The MAP sequential detection of optical signals is investigated. The problem is reduced to the N-ary orthogonal signal detection problem in which the counts measured are conditionally Poisson distributed. The MAP sequential data processing algorithm is synthesized, and its performance bounds are found. The results obtained are verified by means of computer simulation. The performance of the sequential algorithm is compared with that of the fixed-sample-size-algorithm. It is shown that the MAP sequential algorithm demands a substantially smaller average signal energy than the fixed-sample-size algorithm to achieve the same error probability.     

级联光参量振荡与放大技术研究进展

高性能中红外激光源在科研、民用及军事对抗等领域具有重要的应用价值。级联光参量振荡与放大技术可以显著提高抽运光子利用率,是获取高转换效率、高光束质量和系统高度集成中红外激光的有效方式。介绍了级联光参量振荡与放大技术的基础理论、典型结构以及常用非线性光学晶体,评述了级联光参量振荡与放大技术的研究进展,分析了级联光参量振荡与放大技术在非线性晶体制备、废热管理和镀膜工艺等方面面临的挑战,并对这项技术的发展趋势进行了展望。     

Generalized OSTBC‐based subcarrier intensity‐modulated MIMO optical wireless communication system

In this paper, we analyze an optical wireless communication (OWC) system having a source and a destination node, equipped with multiple transmit and receive apertures, respectively. We utilize generalized orthogonal space‐time block codes (OSTBCs) of any arbitrary order and subcarrier intensity modulation scheme for data transmission over gamma–gamma (GG) fading optical links using M ‐ary phase‐shift keying (PSK) constellation. A symbol‐wise decoding is utilized, and the closed‐form expression of the approximate average symbol error rate (SER) of multi‐aperture‐based OWC system is obtained for the generalized OSTBC and an arbitrary M ‐PSK constellation. Using the derived SER expression, we analytically evaluate the diversity order and the coding gain of the OWC system with GG atmospheric turbulence. It has been shown by the numerical results that the maximum possible diversity is achieved by using the symbol‐wise maximum likelihood decoding in the destination. Copyright © 2016 John Wiley & Sons, Ltd.     

Figure of merit for envelope detection of optical signals

A figure of merit is defined which may be applied to any of the common types of optical-envelope detectors such as photo-multipliers and photodiodes. It is evaluated for two special groups: (a) when the amplifier noise and dark current are negligible, and (b) when the quantum-noise term is negligible.     

Digital coherent receiver for subcarrier multiplexed phase-modulated radio-over-fibre signals

Digital coherent detection of multi-channel subcarrier multiplexed optically phase-modulated radio-over-fibre signals is experimentally demonstrated. Successful detection after transmission over a 40 kmlong fibre link of four or five 25 Mbaud BPSK/QPSK subcarrier channels in 5 GHz bandwidth is demonstrated using offline digital signal processing.     

1.25-Gb/s bidirectional colorless WDM-PON based on RSOA using subcarrier detection and optical carrier suppression

A new architecture for bidirectional gigabit colorless wavelength division multiplexed-passive optical network system based on a reflective semiconductor optical amplifier is proposed. It uses techniques of both optical carrier suppression and subcarrier multiplexing. There is no impact of a downlink signal on an uplink one due to the wavelength reuse because a light from a single optical source is divided into two parts for uplink and downlink transmissions. One is modulated by a downlink signal and the other, which is transformed into two sidebands with a suppressed optical carrier, is utilized for an uplink transmission. An uplink data is recovered by subcarrier multiplexing technique. 1.25-Gb/s error-free transmissions of both uplink and downlink are demonstrated experimentally.