Speed Optical Fiber Communication Systems Research Articles

Signal recovery based on optoelectronic reservoir computing for high speed optical fiber communication system

Signal recovery effects of a channel equalization method based on optoelectronic reservoir computing (RC) are investigated for actual high speed optical fiber communication systems. The RC is implemented numerically by using a Mach–Zehnder intensity modulator with an optoelectronic delay feedback loop. Two optical communication systems with different transmission distances and receivers based on 25G-class optics are built in-lab. 50-Gb/s non-return-to-zero (NRZ) and four-level pulse amplitude modulation (PAM4) signals transmitted by the two systems are recovered by using optoelectronic RC and different combinations of feed-forward equalizer (FFE) with decision feedback equalizer (DFE) and maximum likelihood sequence estimation (MLSE), respectively. Under the same conditions, optoelectronic RC is better than FFE&DFE, and far superior to FFE&MLSE in the equalization performances. When the receiver is a positive–intrinsic–negative or avalanche photodiode, for the NRZ signal, compared with 45-tap FFE and 9-tap DFE, the sensitivity is increased by ∼3.2/3.4 dB; for the PAM4 signal, the sensitivity is improved by ∼4.9/4.6 dB compared with 123-tap FFE and 9-tap DFE. These experimental results show that the optoelectronic RC has excellent performances for signal recovery of different modulation formats and transmission systems.

A class of orthogonal polynomials related to the generalized Laguerre weight with two parameters

We investigate a sequence of polynomials orthogonal with respect to the weight function, which appears in the error statistics in high speed optical fiber communication systems. Computation of these integrals by classical approach shows unexpectedly dubious accuracy. That is why we had to construct the new quadratures, to get more reliable results in our applications. Numerical procedure for quadrature construction is considered and its stability is discussed in detail.

Demonstration of Multimode Optical Fiber Communication System using 1300 nm Directly Modulated VCSEL for Gigabit Ethernet

In the recent years, the optical networks have grown to unexpected dimensions. The growth of active users and growing demand for data services set high requirements to network providers. Driving forces of this growth are multimedia, cloud computing and web services which set high bandwith demand. The majority of currently deployed optical networks utilize passive or active network structure using dominantly singlemode optical fiber (SMF). SMF is believed to be the better choice over multimode optical fiber (MMF) for high speed optical fiber communication systems. And in some applications it definitely is. MMF has found use especially for short distance communication as it easily supports distances required for interconnecting building, data centres or campuses. In this paper we present a simulation model of 1000BASE-LX Ethernet with MMF using different optical modulation techniques. The aim of this article is to demonstrate possibilities of MMF based 1000BASE-LX Ethernet with directly modulated vertical-cavity surface-emitting laser (VCSEL).

Broadband Dispersion Compensation Technology in High Speed Optical Fiber Communication Systems

Broadband Dispersion Compensation Technology in High Speed Optical Fiber Communication Systems

A novel multilevel coding technique for high speed optical fiber communication systems

This paper delineates a novel coding technique, a combination of coding and multiplexing technique, known as mapping multiplexing technique (MMT). A mapping algorithm is used to multiplex four channels, each of which running at 10Gbit/s. Up to four bits per symbol at a symbol rate of 10Gboud was successfully transmitted over a single wavelength. Compare to the conventional return to zero (RZ) and none-return to zero (NRZ)-time division multiplexing (TDM) more than 75% and 50% reduction in the spectral width are achieved, respectively. Calculated chromatic dispersion tolerance of ±130ps/nm is achieved for the 40Gbit/s MMT transmission system at the expense of ∼2dB degradation in the receiver sensitivity (compared to NRZ) due to an increase in the number of levels and in the signal dependency of signal-spontaneous beat noise. In comparison with conventional 4-ary system, the proposed system depicts ∼6.5dB improvement in terms of receiver sensitivity.

使用调制相移法测量光纤色散的研究

光纤通信已经成为目前通信网络发展的主流方向。但是随着光纤通信系统向着超远距离、超大容量、超高速率的方向发展，光纤色散已经成为其巨大的阻碍。如何有效地控制光通信系统中产生的色散，使光信号在大容量、高速率、长距离传输中无误码地到达接收端，已经成为人们迫切需要解决的问题。对光通信系统中的色散进行监测并进行动态补偿的研究，使得超大容量、超长距离、超高速率的光纤通信系统成为可能，有助于最终实现全光智能自动交换网络。在众多测量光纤色散的方法中，调制相移法具有结构简单，可靠性强等优点。本文中，我们对使用调制相移法测量光纤色散进行了研究和仿真，讨论了在不同光纤长度和不同调制频率下，影响调制相移法测量结果精度的因素。通过适当地选取调制频率，我们可以使用调制相移法测得不同光纤长度下色散的精确值。另外在本文中，我们通过仿真验证了调制相移法可以测量具有任意色散–波长曲线的光纤。因此在实际应用中，调制相移法是可以应用于高精度光纤色散的测量。 Optical fiber communication is the mainstream of communication development at present. However, with the development of optical fiber communication system which trending towards ultra-long length, ultra-large capacity and ultra-high speed, fiber dispersion turned to be a great obstacle. How to control the dispersion created in the optical communication system effectively while force optical signal to reach the receiving end in high-capacity, high-rate and error-free long-distance transmission has increasingly become a research focus of optical fiber communication systems. It is a great significance to research about monitor and dynamic compensate dispersion in the optical communication systems, so that the ultra-large capacity, ultra-long length and ultra-high speed optical fiber communication systems would not be impossible, all-optical intelligent network with automatic switching functions would come true. Among the varieties of methods to measure fiber dispersion, the phase-modulation shift method is the unique one, which has the advantages of simple structure, high reliability. In this paper, we make a research and simulate to use the phase-modulation shift method, meanwhile we also discuss about the factors which affect the accuracy of the results in the different fiber lengths and modulation frequencies. By the means that selecting appropriate modulation frequency, we can use modulation phase shift method to measure the exact value of dispersion comes out from different lengths of fiber. Moreover, this paper also proves that the phase-modulation shift method is able to measure the optical fiber with arbitrary dispersion-wavelength curve, which is already verified by our simulation. Therefore, the phase-modulation shift method is well to be applied to take practice in the high-precision fiber dispersion measurement.