Further Theoretical Investigations for Laser Relative Intensity Noise with Fiber Nonlinearities and Higher-Order Dispersion

In this article, we theoretically investigate relative intensity noise (RIN) in optical communication systems with fiber nonlinearities due to optical Kerr effects and higher-order dispersion. The impact of modulation frequencies, launch power, and laser bias current on RIN has been illustrated. We show that RIN increases with modulating frequencies up to the resonance frequency, launch power, and decrease in the laser bias current. We also show that higher-order dispersion terms have no impact on the RIN, but with first-order dispersion compensation the higher-order dispersion terms have significant impact at high modulating frequencies. The RIN with and without fiber nonlinearities is further investigated. It has been shown that the RIN with fiber nonlinearity is more than the RIN without nonlinearity and the effect of nonlinearity appears at higher modulation frequencies only.     

Further Theoretical Investigations for Laser Relative Intensity Noise with Fiber Nonlinearities and Higher Order Dispersion

In this article, we theoretically investigate relative intensity noise (RIN) in optical communication systems with fiber nonlinearities due to optical Kerr effects and higher order dispersion. The impact of modulation frequencies, launch power, and laser bias current on RIN has been illustrated. We show that RIN increases with modulating frequencies up to the resonance frequency and launch power, and decreases in the laser bias current. We also show that higher order dispersion terms have no impact on the RIN, but with first order dispersion compensation the higher order dispersion terms have significant impact at high modulating frequencies. The RIN with and without fiber nonlinearities is further investigated. It has been shown that the RIN with fiber nonlinearity is more than the RIN without nonlinearity and the effect of nonlinearity appears at higher modulation frequencies only.     

Further Theoretical Investigations for Laser Relative Intensity Noise with Fiber Nonlinearities and Higher Order Dispersion

In this article, we theoretically investigate relative intensity noise (RIN) in optical communication systems with fiber nonlinearities due to optical Kerr effects and higher order dispersion. The impact of modulation frequencies, launch power, and laser bias current on RIN has been illustrated. We show that RIN increases with modulating frequencies up to the resonance frequency and launch power, and decreases in the laser bias current. We also show that higher order dispersion terms have no impact on the RIN, but with first order dispersion compensation the higher order dispersion terms have significant impact at high modulating frequencies. The RIN with and without fiber nonlinearities is further investigated. It has been shown that the RIN with fiber nonlinearity is more than the RIN without nonlinearity and the effect of nonlinearity appears at higher modulation frequencies only.     

Femto-Second Transform Limited Pulse Generation with Higher Order Dispersion Effects for Dispersion-Shifted Optical Communication System

The paper deals with the influence of higher-order effects of dispersion on the femto-second transform limited pulse generation by compensating for linear chirp of self-phase modulation spectra in the dispersion-shifted fibers. It has been shown that the minimum propagation length with first-order dispersion term is 23 m, as reported earlier. If the higher-order dispersion effects are taken into consideration, this length is reduced to 11.5 m. With compensation of the first-order dispersion term, this length can be enhanced to 6.8161 × 10³ km. This length can further be improved to 6.0343 × 10⁹ km by compensation of first- and second-order dispersion terms together. The minimum pulse width and linewidth product without dispersion, with dispersion including higher-order dispersion effects, and with dispersion compensation, is found to be 0.44, 0.4418, and 0.4411, respectively.     

Femto-Second Transform Limited Pulse Generation with Higher Order Dispersion Effects for Dispersion-Shifted Optical Communication System

The paper deals with the influence of higher-order effects of dispersion on the femto-second transform limited pulse generation by compensating for linear chirp of self-phase modulation spectra in the dispersion-shifted fibers. It has been shown that the minimum propagation length with first-order dispersion term is 23 m, as reported earlier. If the higher-order dispersion effects are taken into consideration, this length is reduced to 11.5 m. With compensation of the first-order dispersion term, this length can be enhanced to 6.8161 × 10³ km. This length can further be improved to 6.0343 × 10⁹ km by compensation of first- and second-order dispersion terms together. The minimum pulse width and linewidth product without dispersion, with dispersion including higher-order dispersion effects, and with dispersion compensation, is found to be 0.44, 0.4418, and 0.4411, respectively.     

Approximate and Exact Small Signal Analysis for Single-Mode Fiber Near Zero Dispersion Wavelength with Higher Order Dispersion

This article presents the comparison of approximate and exact small-signal theories for analyzing the influence of the higher-order dispersion terms on dispersive optical communication systems operating near zero dispersion wavelength for linear single-mode fiber. For the approximate theory, the generalized conversion matrix has been reported and gives the transfer function of intensity and phase from the fiber input to fiber output for a laser source including the influence of any higher-order dispersion term. In addition, expressions for the small-signal frequency response and the relative intensity noise (RIN) response of an ultrafast laser diode including noises are derived. However, it is observed that the approximation assumed for the second-order dispersion term for the approximate analysis is not valid. From the approximate theory, the exact generalized conversion matrix and exact expressions for small-signal frequency response and relative intensity noise (RIN) are obtained. We show that for the exact theory, the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances contrary to the approximate theory as reported by other authors. But we show that third-order dispersion term certainly has some minute impact on the frequency and RIN response for long distance links at high modulating frequencies.     

Approximate and Exact Small Signal Analysis for Single-Mode Fiber Near Zero Dispersion Wavelength with Higher Order Dispersion

This article presents the comparison of approximate and exact small-signal theories for analyzing the influence of the higher-order dispersion terms on dispersive optical communication systems operating near zero dispersion wavelength for linear single-mode fiber. For the approximate theory, the generalized conversion matrix has been reported and gives the transfer function of intensity and phase from the fiber input to fiber output for a laser source including the influence of any higher-order dispersion term. In addition, expressions for the small-signal frequency response and the relative intensity noise (RIN) response of an ultrafast laser diode including noises are derived. However, it is observed that the approximation assumed for the second-order dispersion term for the approximate analysis is not valid. From the approximate theory, the exact generalized conversion matrix and exact expressions for small-signal frequency response and relative intensity noise (RIN) are obtained. We show that for the exact theory, the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances contrary to the approximate theory as reported by other authors. But we show that third-order dispersion term certainly has some minute impact on the frequency and RIN response for long distance links at high modulating frequencies.     

初始啁啾补偿光纤色散效应的适用范围

以啁啾高斯脉冲在单模光纤中的传输为例,分别就线性初始啁啾对光纤二阶和三阶色散的补偿进行了系统的理论分析和数值计算,结果表明：线性初始啁啾对光纤的二阶色散（线性色散）有一定的补偿作用,但不能有效地用于三阶色散的补偿.     

Large Signal Analysis of FM-AM Conversion in Dispersive Optical Fibers for PCM Systems Including Second Order Dispersion

By using large signal analysis for dispersive optical fiber, the FM-AM conversion with respect to binary intensity modulated PCM systems including second order dispersion term is discussed. The modified expression for power penalty has been derived and its impact on laser linewidth and bit rate has been investigated. For power penalty less than 0.5 dB, the plots between bit rate and transmission distance are plotted. It is seen that the transmission distance increases with decrease in linewidth over significant bit rates. The transmission distance with first order dispersion term for 300 MHz linewidth is approximately 800km. With proper first order dispersion compensation, i.e., with second order dispersion only, the transmission distance can be enhanced to 10 8 km for this linewidth. The linewidth requirements for systems with different bit rates and transmission distances are also calculated and discussed. Further, it is seen that by including the second-order dispersion term, the bit rate and transmission distance decreases. For higher linewidths, this decrease in bit rate and transmission distance is very less and vice versa. For 300 MHz linewidth, the decrease in transmission distance is just 30 km, and for 30 MHz linewidth, the decrease is approximately 600 km over significant bit rates.     

Numerical Study on the Performance in High-bit-rate Optical Communication Systems

By numerical simulations, we show that picosecond Gaussian optical pulses with a precise optimal frequency chirping can transmit stably in full-dispersion compensation optical fiber links, with not only second- but also third-order dispersion compensation, using dispersion shift fibers with opposite dispersion sign. The optimal pre-chirp is determined principally by the second-order dispersion scheme and scarcely affected by third-order dispersion scheme. It demonstrates that, to a high bit rate transmission system, the pre-chirping technology and higher-order dispersion compensation are two very efficient measures in improving performance of system.     

Relative Intensity Noise in Optical Single Side Band Systems with Multiple In-Line Amplifiers: Analysis and Validation

This article analyzes and validates through simulation the influence of fiber nonlinearity, dispersion, and loss on the Relative Noise Intensity (RIN) spectrum at fiber output in externally modulated optical single side band (OSSB) systems. The analysis includes the RIN generated by the laser source, the effect of the OSSB modulator, and noise generated by the in-line optical amplifiers. The analysis takes into account conversion between phase noise and intensity noise introduced by fiber transmission. It is shown that, depending on the operating conditions, the system performance may be predominantly affected either by the laser RIN or by the noise generated by the in-line optical amplifiers. The impact of the OSSB modulator can be relevant when the RIN of the system is dominated by the laser noise and should therefore be considered.     

Relative Intensity Noise in Optical Single Side Band Systems with Multiple In-Line Amplifiers: Analysis and Validation

Abstract

This article analyzes and validates through simulation the influence of fiber nonlinearity, dispersion, and loss on the Relative Noise Intensity (RIN) spectrum at fiber output in externally modulated optical single side band (OSSB) systems. The analysis includes the RIN generated by the laser source, the effect of the OSSB modulator, and noise generated by the in-line optical amplifiers. The analysis takes into account conversion between phase noise and intensity noise introduced by fiber transmission. It is shown that, depending on the operating conditions, the system performance may be predominantly affected either by the laser RIN or by the noise generated by the in-line optical amplifiers. The impact of the OSSB modulator can be relevant when the RIN of the system is dominated by the laser noise and should therefore be considered.     

Linewidth and relative intensity noise measurements of longitudinal modes in ultrahigh-speed mode-locked laser diodes

The longitudinal linewidth and corresponding relative intensity noise (RIN) of 10- and 40-GHz mode-locked laser diodes are measured for the first time to our knowledge. It is shown that the cavity Q value is a dominant parameter of the linewidth. It is also shown that the linewidth of the individual modes is almost constant. This means that the phase noise of each mode is almost the same in the mode-locked condition. The RIN value is larger for modes that are distant from the center longitudinal mode. This mode dependence is a consequence of the mode partition noise.     

Optical Fiber Impulse Propagation: An Interaction Between the Third-Order Dispersion and Nonlinear Chirp

This article investigates the interaction between the third-order dispersion in optical fiber and the nonlinear (quadratic) chirp of Gaussian impulses. A formula is obtained for the impulse form at the fiber far end. The impulse propagation in nonlinear fiber is also examined by means of a computer simulation. The obtained results indicate that the interaction may lead to significant distortion of optical impulses at the fiber output even when the second-order dispersion is entirely canceled and the input impulse has no linear chirp. This distortion is more pronounced when the dispersion slope, fiber length, and nonlinear chirp parameter increase.     

通信系统中色散补偿光纤的研究

对五包层色散补偿光纤进行了研究,分析了各个参量对色散补偿光纤性能的影响,发现色散补偿光纤只有在一定范围的拉丝芯径内,以牺牲负色散数值为代价才能获得较大的负色散斜率。在1550nm处获得了不大于150ps/(nm·km)的负的总色散和负色散斜率的色散补偿光纤。采用在光纤拉丝时旋转预制棒的工艺减小了光纤的偏振模色散,并采用化学汽相沉积(MCVD)光纤生产工艺,研制出了性能较好的色散补偿光纤。     

Analytical investigations on crosstalk in fiber Raman amplification for WDM systems

In this paper, the analytical investigations for the crosstalk in fiber amplification for WDM channels have been reported. The crosstalk between WDM channels with external Raman amplification including second-order dispersion terms has been investigated. It has been shown that the higher-order dispersion severely degrades the performance of optical communication systems. To ensure small crosstalk, the signal gain and the injected pump power should be limited to the value well below the threshold of Raman amplification. Analytical formula for signal interference ratio (SIR) and gain in fiber Raman amplifier including the impact of second-order dispersion terms for WDM systems has been derived at different wavelengths. It has also been shown that there is increase in crosstalk due to second-order dispersion.     

Minimization of self-steepening of ultra short higher-order soliton pulse at 40 Gb/s by the optimization of initial frequency chirp

In this paper, the decay of first- and second-order ultra short pulses of the order of 50 fs due to self-steepening (SS) effect has been numerically investigated for a 40 Gb/s optical soliton system including the impact of third-order dispersion (TOD). It has been observed that the prechirp (both positive and negative) in the pulse can counteract the SS effect and improve compensation performance for the distortions .The critical positive prechirp value is found to be 1.4 and the negative prechirp is 1.2, beyond which the soliton pulse is unstable.     

Analysis of the impact of laser line width over RIN, power penalty and bit rate including higher-order dispersion in WDM systems

This paper investigated the effect of laser line width over relative intensity noise (RIN), power penalty and bit rate at optical distances in the range of 100-10,000 km both analytically and graphically. It is also proposed and analyzed that by reducing the laser line width to the range of KHz, we can minimize the impact of RIN and power penalty under the individual and combined impact of higher-order dispersion parameters.     

40 Gb/s窄脉冲预啁啾归零码色散管理传输

通过数值计算的方法，对40Gb/s带有预啁啾和无啁啾的窄脉冲归零码在色散管理光纤链路中的传输特性进行了比较，计算发现，脉冲的预啁啾会与光纤的高阶色散共同作用，并增强高阶色散对传输的影响，只有在高阶色散得到很好补偿以后，窄脉冲带啁啾的归零码（CRZ）的传输特性才会好于无啁啾的归零码。对不同的入射脉冲条件和传输链路参量存在相应的预啁啾最佳值。     

Analysis and simulation of the effect of spectral width over intensity noise under the impact of higher-order dispersion parameters in the optical communication systems

In this paper, we analyzed the effect of spectral width of different light sources under the individual and combined impact of first- and second-order dispersion parameters both analytically and graphically. This work also covers the amount of intensity noise introduced in an optical system and the power penalty required to compensate this intensity noise at different optical distances. It has been also investigated that reducing the spectral width can minimize the intensity noise and the power penalty under the individual and the combine impact of higher- order dispersion parameters. An experimental set up is also analyzed to support our results.