Maximum Transmission Length Research Articles

Effect of linewidth enhancement factor of laser diode and fiber dispersion management on high-speed optical fiber links performance and use in WDM systems

We present a numerical simulation study on the effect of the linewidth enhancement factor (α) of semiconductor laser and dispersion management methods of optical fibers on the performance of 40-Gb/s directly-modulated fiber links and their application in WDM systems. The dispersion management methods include the use of non-zero dispersion-shifted fiber (NZ-DSF), dispersion-compensating fiber (DCF), and fiber Bragg grating (FBG). The optimal values of the α-parameter and the best dispersion management method are applied to design and simulate a four-channel × 40-Gb/s WDM fiber system. The obtained results show that the increase in the α-parameter and/or fiber length reduces the performance of both the 40-Gb/s optical link and the WDM system. Regarding the 40-Gb/s optical link, when α = 1, using –NZ-DSF or + NZ-DSF, DCF with SSMF, and FBG with SSMF work to increase the transmission length from 1.6 km of a standard single-mode fiber (SSMF) to 7.2, 26.5, and 40 km, respectively. Whereas at α = 3.5, the maximum transmission length reaches 1.2 km when using SSMF, –NZ-DSF, or + NZ-DSF, while it increases to 13 and 35 km when using DCF with SSMF, and FBG with SSMF, respectively. In the designed WDM system, the use of FBG with SSMF is predicted as the most effective method for dispersion management. The maximum transmission length reaches 25 km when α = 1, but reduces to 12 km when α = 3.5.

Impact of linewidth enhancement factor and gain suppression on chirp characteristics of high-speed laser diode and performance of 40 Gbps optical fiber links

We present a simulation study on the chirping characteristics of a directly modulated 40 Gbps laser diode and evaluate its performance for use in high-speed optical fiber links. The effects of the linewidth enhancement factor (α) and gain suppression on the laser chirp and the maximum fiber transmission length are investigated. The chirp characteristics include the frequency peak-to-peak chirp of the time-varying frequency and shift of the emission wavelength. The performance of 40 Gbps optical fiber link is evaluated in terms of the eye diagram and quality factor of the received signal, which helps in predicting the maximum fiber length that achieves error-free transmission. The results show that when α increases from 1 to 10, the overshoots of the relaxation oscillations become strong, resulting in a sharp increase in laser peak-to-peak chirp from 21.8 to 205 GHz. The increase of gain suppression factor form ε = 0.5 × 10–17 cm3 to ε = 5 × 10–17 cm3 dampens out the overshoots and slightly reduces the peak-to-peak chirp from 19.5 to 193.3 GHz. Although the gain suppression works to reduce the laser chirp, it causes a significant wavelength shift relative to the emission wavelength of the non-modulated laser, which degrades the efficiency of the laser diode. On the other hand, the gain suppression is shown to increase the degree of eye-opening and the corresponding Q-factor of the fiber link on a reverse action of the linewidth enhancement factor. As fiber length increases, the influences of α and ε on chirp characteristics become more significant. The maximum fiber length (Lmax) is shown to decrease with the increase in α and/or ε; when α increases from 1 to 10, Lmax decreases from 5.89 to 0.78 km at ε = 5 × 10–17 cm3, and decreases from 2.52 to 0.3 km at ε = 0.5 × 10–17 cm3.

Analytical evaluation of combined influence of XPM, ASE and SRS in a Raman amplifier based WDM system

A novel analytical technique is developed to assess the performance of a WDM transmission system taking into account the combined influence of XPM, SRS and ASE induced crosstalk. Performance results are determined in terms of BER due to collective impact of SRS, ASE and XPM effect for different system parameters viz. WDM channel number, channel spacing, pump power and fiber length. It is noticed that BER is highly affected due to the influence of above limitations and system suffers significant power penalty at a given BER of 10−9. It is found that at BER of 10−9, power penalty is 24 dB and 26 dB for 4 and 8 number of WDM channel respectively with 10 Km fiber length and channel bandwidth 12.5 GHz. It is further observed that the maximum acceptable transmission length at a BER of 10−9is found to be 58 km and 45 km corresponding to channel bandwidth of 12.5 GHz and 25 GHz respectively for number of WDM channel number is 4. Analytical results are found to be in conformity with results published in literature.

0.55 Tb/s heterogeneous Nyquist-WDM superchannel using different polarization multiplexed subcarriers

This paper depicts the design of 0.55 Tb/s heterogeneous Flexi-rate Nyquist-wavelength division multiplexed (Nyquist-WDM) Superchannel. Here, for the first time, four subcarriers of different modulation formats are accommodated, namely polarization multiplexed-binary phase-shift keying, polarization multiplexed-quadrature phase-shift keying (PM-QPSK), polarization multiplexed-8-quadrature amplitude modulation and PM-16QAM, each with 27.75 Gbaud symbol rate. The system transmission performance with acceptable bit error rate (BER) 4 × 10−3 is analyzed over pure silica core fiber (PSCF) in the presence of hybrid optical amplification, i.e., Raman amplifier along with a counter-propagating pump and Erbium-doped fiber amplifier. The presence of this hybrid optical amplification unit results in a limited optical signal-to-noise ratio requirement and makes the whole system cost-effective. The proposed work delivers excellent spectral efficiency of 4.5 b/s/Hz and highest transmission reach of 5500 km for PM-QPSK subcarrier and 2300 km for PM-16QAM subcarrier in the presence of PSCF. The system performance against intersymbol interference and noise is also analyzed with the aid of eye pattern plot at a minimum and maximum transmission length.

Ultralong single-span lines with remote pumping of optical amplifiers

Methods for estimation of the maximum transmission length of the DWDM signals in single-span lines with different configurations are proposed. A transponder that works at a bit rate of 100 Gb/s using the dual-polarization quadrature phase-shift keying (DP-QPSK) is used as an example to present the maximum lengths of the single-span lines with different configurations. The estimations are used to experimentally demonstrate that a transceiver with the above modulation and coherent detection and soft-decision forward error correction (SoftFEC) and an ultralow-loss fiber make it possible to reach a transmission length of greater than 500 km for the DWDM signals at a channel bit rate of 100 Gb/s.

800 Gb/s (80 × 10 Gb/s) capacity WDM-PON based on ASE injection seeding.

We demonstrate and characterize 800 Gb/s capacity WDM-PON with an ASE injection seeding. Required total seed power at central office to feeder fiber is 16 dBm for 20 km upstream transmission of 80 channels. We investigate the maximum transmission length according to channels. The transmission length is limited to 39.7 km by intra-channel crosstalk induced by Rayleigh back-scattering, provided that the dispersion is compensated. Also, we investigate the allowable differential path length to evaluate the flexibility of the system.

A Comprehensive Model for Performance Analysis of APD-based FSO Systems using M-PPM Signaling in Atmospheric Turbulence

In this paper, a model of Gaussian pulse propagation over atmospheric turbulence channel is used to comprehensively analyze the performance of APD-based free-space optical communication (FSO) systems using M-PPM signaling. This model is able to simultaneously take into account all effects of atmospheric turbulence including attenuation, intensity fluctuation, and pulse broadening, which has not been considered in previous works. In addition, the impacts of APD shot noise, background noise, and thermal noise are included in our analysis. The numerical results show that the main factor that limits the system performance is intensity fluctuation. However, when M is large enough, optical pulse is so short that the effect of pulse broadening becomes dominant. By using APD receiver, bit-error rate is improved significantly. Finally, based on channel capacity, we are able to determine the maximum transmission length of the system.

Performance Analysis of Spectral Amplitude Encoding OCDM Systems Over a Linear Dispersive Optical Channel

We propose a new model of pulse propagation over a linear dispersive optical channel and use this model to comprehensively analyze the performance of spectral amplitude encoding optical code-division multiplexing (SAE/OCDM) systems under the impact of group velocity dispersion (GVD). We quantitatively discuss the impact of GVD on various aspects of SAE/OCDM system performance, including the number of supportable users and the maximum transmission length and power penalty. We also investigate the system performance with several types of optical fibers, such as single-mode fiber (SMF), dispersion-shifted fiber (DSF), and nonzero DSF. In addition, we discuss techniques to compensate for GVD so that the performance of SAE/OCDM systems can be improved.

Impact of GVD on the Performance of 2-D WH/TS OCDMA Systems Using Heterodyne Detection Receiver

SUMMARY In this paper, a novel model of Gaussian pulse propagation in optical fiber is proposed to comprehensively analyze the impact of Group Velocity Dispersion (GVD) on the performance of two-dimensional wavelength hopping/time spreading optical code division multiple access (2-D WH/TS OCDMA) systems. In addition, many noise and interferences, including multiple access interference (MAI), optical beating interference (OBI), and receiver’s noise are included in the analysis. Besides, we propose to use the heterodyne detection receiver so that the receiver’s sensitivity can be improved. Analytical results show that, under the impact of GVD, the number of supportable users is extremely decreased and the maximum transmission length (i.e. the length at which BER ≤ 10−9 can be maintained) is remarkably shortened in the case of normal single mode fiber (ITU-T G.652) is used. The main factor that limits the system performance is time skewing. In addition, we show how the impact of GVD is relieved by dispersion-shifted fiber (ITU-T G.653). For example, a system with 32 × 1G bit/s users can achieve a maximum transmission length of 111 km when transmitted optical power per bit is − 5d Bm.

First Experimental on OXADM Restoration Scheme Using Point-to-Point Configuration

This paper introduces a new optical device model named as Optical Cross Add and Drop Multiplexer (OXADM) which is potentially useful in CWDM metro area network. The device uses the combined concepts of optical add/ drop multiplexing and optical cross connect between two main transmission lines in order to implement the wavelength routing operation [10]. Thermal-optical switches are integrated in the device to make it re-configurable. With its excellent features, the device is particularly designed to improve the network efficiency, flexibility and survivability [7, 8]. The device can be used in point-to-point, ring or mesh network topology to provide functionalities such as routing, supervision, transport, multiplexing and restoration of client digital signals processed predominantly in the optical domain [7]. The wavelengths on each optical trunk can be switched into each other while implementing add and drop functions simultaneously. The paper highlights on first experimental work on 2x2 OXADM prototype to measure OSNR values for single operation of OXADM. The results show the condition is in safe with (OSNR>20dB) for every function of OXADM. With 6 dB insertion loss, the maximum achievable transmission length by the OXADM is 71 km without amplification and the maximum achievable node is 6 units.

Optical Cross Add and Drop Multiplexer (OXADM) in CWDM Ring Network

This paper introduces a new optical device model named as Optical Cross Add and Drop Multiplexer (OXADM) which is potentially useful in CWDM metro area network. The device uses the combined concepts of optical add/drop multiplexing and optical cross connect between two main transmission lines in order to implement the wavelength routing operation [10]. MEMs optical switches are integrated in the device to make it re-configurable. With its excellent features, the device is particularly designed to improve the network efficiency, flexibility and survivability [7, 8]. The device can be used in point-to-point, ring or mesh network topology to provide functionalities such as routing, supervision, transport, multiplexing and restoration of client digital signals processed predominantly in the optical domain [7]. The wavelengths on each optical trunk can be switched into each other while implementing add and drop functions simultaneously. The multiplexer has undergone performance test at 2.5 Gbit/s (OC-48) with BER less than 10 -9 . The maximum achievable transmission length by the OXADM is 71 km without amplification with insertion loss of 6 dB.

Dense WDM-PON based on wavelength-locked Fabry-Pe/spl acute/rot laser diodes

We demonstrate a bidirectional 12-channel wavelength-division-multiplexing passive optical network (WDM-PON) with 50-GHz channel spacing based on wavelength-locked Fabry-Pe/spl acute/rot laser diodes. The maximum transmission length is 30 km including 20 km of feeder fiber and 10 km of distribution fiber. The proposed WDM-PON system can accommodate 80 channels with erbium-doped fiber amplifier-based broad-band light sources. We also propose a few methods for the wavelength-independent operation of an optical network termination.

A microwave coherence‐multiplexed optical transmission system on Ti:LiNbO3 integrated optics technology

A high-speed experimental optical coherence multiplexing system is proposed here. The system consists of a two-channel serial coherence multiplexed architecture with single-mode fiber and Ti:LiNbO3 integrated optics technology. The optical link has been tested by transmitting two simultaneous microwave analog signals through a 2.5-km optical fiber channel. Reported performances of the experimental coherence multiplexing modulation include optical power budget, maximum transmission length, optoelectronic bandwidth, and cross talk. © 1997 John Wiley & Sons, Inc.

Experimental investigation of Gordon-Haus limit on soliton transmission by using optical short pulses generated by an InGaAsP electroabsorption modulator

The maximum transmission length of data coded solitons at 5Gbit/s has been investigated for a simple Er-doped fibre amplifier system without in-line soliton controls using short pulses generated by an InGaAsP electroabsorption modulator. The use of low fibre dispersion and large separation of solitons was effective in increasing the transmission distance up to 13100km with less than 10−9 bit error rate. The obtained transmission capacity of 65 Tbit/s km is the largest reported for soliton transmission experiments without soliton control.

SELF-CONSISTENT PUMP DEPLETION METHOD TO DESIGN OPTICAL TRANSMISSION SYSTEMS AMPLIFIED BY BIDIRECTIONAL RAMAN PUMPS

The self-consistent pump depletion (SCPD) method is proposed to numerically solve the complete set of the coupled equations governing the signal and Raman pump powers in the unidirectional and bidirectional signal transmission systems. The maximum transmission lengths under the requirement of some minimum signal power for unidirectional and bidirectional signal transmission systems are studied. It is found that the maximum length decreases as the bit rate increases. With the same fiber loss of the signal wave, the optimum pump power and maximum transmission length for different fiber losses of the pump waves are shown for 1 Gbits/sec transmission system.

Signal linewidth broadening due to nonlinear Kerr effect in long-haul coherent systems using cascaded optical amplifiers

Signal spectral linewidth broadening due to the interaction between nonlinear Kerr effect and spontaneous emission from optical amplifiers in long-haul coherent optical fiber communication systems using optical amplifiers is examined theoretically and experimentally. By theoretical consideration and recirculating-loop experiments, it is shown that this effect becomes an essential limitation on maximum transmission length in transoceanic coherent optical fiber submarine cable systems. >

Noise properties of a bidirectional optical fiber transmission system using Raman amplifers

Abstract Noise properties of a bidirectional optical fiber transmission system using Raman amplification are analyzed. Analytical expressions for both forward and backward amplified spontaneous emission (ASE) noise are established in terms of system parameters. The signal to ASE noise ratio (SNR) and the achievable repeater length are discussed. Based on the results, we find that there exist optimum pump and initial power levels for the maximum SNR and repeater spacing. The maximum system transmission length and accumulated ASE noise for a multiple‐amplifier system are calculated. A maximum system transmission length up to 5,000 km with 12 dB SNR is then predicted.

Bidirectional optical fiber transmission systems using Raman amplification

Bidirectional optical fiber transmission systems using Raman amplification are discussed. Analytical expressions for signals amplified by both forward and backward Raman scattering are presented. It is found that there exists an optimal pump power for the maximum unrepeated transmission length in a bidirectional system and that the maximum length is about 450 km, which is about the same as that of the unidirectional system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Stimulated Raman scattering in optical fibres: the design of distortion-free transmission

A method for the design of a source, fibre and detector system, which is free from distortion due to stimulated Raman scattering, is proposed. The maximum transmission length and optimum loss value are predicted for a known input power level in dimensionless plots which clearly distinguish the operating region free of stimulated Raman scattering. Circumstances in which the losses at the pump and Stokes wavelengths are unequal are considered.