Raman EDFA Research Articles

Optimization of hybrid amplifier parameters for improved optical link performance

In this manuscript, the gain of the EDFA-Raman hybrid optical amplifier (HOA) is maximized using a popular nature inspired Whale Optimization Algorithm (WOA). The dominating parameters of HOA, length of Raman amplifier and EDFA and its pump powers are optimized to get the maximum possible gain. Further, the performance of WOA is compared by using other metaheuristic techniques such as Real coded Genetic Algorithm, Differential Evolution, Particle Swarm Optimization, to optimize the same model of HOA. WOA proves to be a better optimization technique as it is able to find maximum gain, have a better convergence curve and box plot performance as compared to the other three techniques. Moreover, the gain flatness and noise figure performance of HOA is compared with EDFA and Raman amplifier.

Performance Analysis of Different Modulation Techniques for Super Dense System with RAMAN–EDFA–RAMAN HOA

This paper has shown the analysis of 380 × 10 Gbps super dense wavelength division system using different modulation formats such as non-return to zero (NRZ), Electro absorption modulator (MZM), Mach–Zehnder modulator (MZM), return to zero (RZ) and differential phase shift keying for the features of quality factor (Q-factor), bit error rate (BER), output power and eye closure respectively. Amplification has maintained with the help of RAMAN–EDFA–RAMAN hybrid optical amplifier (HOA) for super dense system. Recorded results from NRZ declare to maintain better super dense optical communication with acceptable rating features in terms of Q-factor, BER, output power and eye closure for the distance of 50 to 400 km and 60 to 360 km respectively.

Impact of hybrid optical amplifier for multitudinous segment for super-dense multiplexing system

In this paper, we have investigated the impact of proposed hybrid optical amplifiers (HOAs) in terms of acceptable values of gain, noise figure and OSNR, respectively. Combinations of RAMAN–EDFA HOA, EDFA–SOA HOA and EDFA have arranged in three segments to maintain the best rating for long-haul 400 × 10 Gbps super-dense wavelength division multiplexing (SD-WDM) optical communication system with channel spacing of 6.25 GHz. Flat gain of 25 dB with least variations of 1.5 dB has archived. Also, noise figure of 3.2 dB has recorded without using any cost influence techniques.

Experimental Evaluation of HOA in Terms of Flat Gain in C-Band for Super Dense Optical Communication System

The impact of RAMAN–EDFA hybrid optical amplifier (HOA) in C-band for 80 × 10 Gbps super dense wavelength division multiplexing (SD-WDM) system with the channel spacing of 12.5 GHz is analyzed. A flat gain of (> 17 dB) is obtained with suitable pump power of HOA in the wavelength range from 1545 nm to 1565 nm with less variation of 5 dB. Further, the performance of the proposed system is also evaluated in term of acceptable flattened gain without using any cost effective technique. The recorded value of crosstalk (< 10−1) and power penalty (− 0.5) dB are also supported to maintain long haul super dense optical communication.

A long single-span dispersion-decreasing-like fiber transmission system

We propose a novel unrepeated long single-span front-haul transmission system based on dispersion-decreasing-like fibers (DDLF). The modulation format is 160Gbps and PM-16QAM. The system transmission performance is effectively improved due to the balance of dispersion and nonlinear effects by using the DDLF, the balance of Raman amplification power and input optical power induced by equalization amplification between Raman amplifier and EDFA. The proposed system can effectively avoid the time delay of signal because of low dispersion of the DDLF system, and compensate the transmission attenuation impairment by employing the first-order Raman amplification at lower input power. The bit error rate (BER) of the system is better than 7% hard-decision forward error correction (FEC) threshold value of 3.8 × 10−3 in a wide range of input optical power. This system can be used in the long single-span front-haul transmission in special application scenarios. At higher input optical power, the nonlinear effect of the DDLF is the dominant factor affecting the performance of the transmission system, and nonlinear effect of the DDLF is increased with the increase of input optical power and Raman pump power, resulting in the system performance deterioration.

Impact of adaptive modulated OOFM signals for SD-WDM system using HOA

In this paper, performances of optical orthogonal frequency division multiplexing (OOFM) signals have been analyzed for super-dense wavelength division multiplexing (SD-WDM) system with the support of RAMAN–EDFA–RAMAN–EDFA hybrid optical amplifier. Acceptable rating outcome has been observed in terms of bit error rate (BER) and signal to noise ratio (SNR) for enhancing the high spectral efficiency.

Mitigate the dominating signals for super dense optical communication using HOA

In this paper, impact of crosstalk and fiber nonlinearities has investigated to enhance the signals strength for 260 channels with the data rate of 10 Gbps. Further, power amplification has also maintained with the arrangement of RAMAN–EDFA–RAMAN hybrid optical amplifier for transmission distance of 65 km. Furthermore, analysis has also observed in terms of received crosstalk and different power level of fiber nonlinearities for channel range from 1 to 260. Channel spacing is also main concerned for super dense optical communication which has also resolved in this proposed simulation model. In this way, it is recommended that this proposed model is really helped out to the network operator to enhance the future super dense optical commutation process.

Performance evaluation of hybrid optical amplifiers in WDM system

There is a huge demand of bandwidth and gain in today’s high tech era. To fulfil this demand proper amplification is required. Hybrid Optical Amplifier made a remarkable change in present optical networks in order to amplify the signals for better performance of a system. In this paper, we have proposed the different configurations of hybrid optical amplifiers for better performance of Wavelength Division Multiplexed (WDM) systems. This paper also provides a crucial insight into the performance of different configurations of hybrid optical amplifiers (such as EDFA–Raman, EDFA–EDFA and SOA–EDFA) at 10 Gbps in WDM systems with 0.4 and 0.8 nm channel spacing. Work capacities of the systems were compared on the basis of various parameters viz., fiber length, dispersion, bit error rate, quality factor, eye diagram and output power. Attempts were taken to design 8 × 10 Gbps Dense Wavelength Division Multiplexed system with reduced channel spacing and 16 × 10 Gbps WDM system with 100 GHz channel spacing. It was assessed that for WDM system with 16 inputs and channel spacing of 0.8 nm, Raman–EDFA configuration gives better results as compared to EDFA–EDFA and SOA–EDFA configurations. Further, it was observed that SOA–EDFA configuration with reduced channel spacing (0.4 nm) provided maximum output power and better eye opening with lowest BER at a distance of 100 km. Moreover, it was seen that with increase in channel dispersion from 2 to 8 ps/nm/km, the quality of the signal started decreasing.

100 km Brillouin optical time-domain reflectometer based on unidirectionally pumped Raman amplification

The sensing distance of the optical time-domain reflectometry (BOTDR) is one of the key parameters for many real applications. In practice, the attenuated stimulating pulse light and its Brillouin scattering signal in the general BOTDR system will become too weak as the sensing fiber goes farther, which limits their uses in certain applications in which the distance to monitor is larger. To enhance the operating range of the BOTDR system, unidirectionally pump Raman amplifier is adopted for amplifying the stimulating pulse light and the scattering signal. Furthermore, our experiments confirm that 100 km sensing is realized by regulating parameters such as the power of Raman pump and EDFA gain.

Modeling of forward pump EDFA under pump power through MATLAB

Optical fiber loss is a limiting factor for high-speed optical network applications. However, the loss can be compensated by variety of optical amplifiers. Raman amplifier and EDFA amplifier are widely used in optical communication systems. There are certain advantages of EDFA over Raman amplifier like amplifying the signal at 1550 nm wavelength at which the fiber loss is minimum. Apart from that there is no pulse walk-off problem with an EDFA amplifier. With the advent of optical amplifiers like EDFA, it is feasible to achieve a high bit rate beyond terabits in optical network applications. In our study, a MATLAB simulink-based forward pumped EDFA (operating in C-band 1525–1565 nm) simulation platform has been devised to evaluate the following performance parameters like gain, noise figure, amplified spontaneous emission power variations of a forward pumped EDFA operating in C-band (1525–1565 nm) as functions of Er3+ fiber length, injected pump power, signal input power, and Er3+ doping density. The effect of an input pump power on gain and noise figure was illustrated graphically. It is possible to completely characterize and optimize the EDFA performance using our dynamic simulink test bed.

Optimizing the Net Gain of a Raman-EDFA Hybrid Optical Amplifier using a Genetic Algorithm

For the first time, a novel analytical model of the net gain for a Raman-EDFA hybrid optical amplifier (HOA) is proposed and its various parameters optimized using a genetic algorithm. Our method has been shown to be robust in the simultaneous analysis of multiple parameters (Raman length, EDFA length, and pump powers) to obtain large gain. The optimized HOA is further investigated at the system level for the scenario of a 50-channel DWDM system with 0.2-nm channel spacing. With an optimized HOA, a flat gain of >17 dB is obtained over the effective ITU-T wavelength grid with a variation of less than 1.5 dB, without using any gain-flattening technique. The obtained noise figure is also the lowest value ever reported for a Raman-EDFA HOA at reduced channel spacing.

Influence of the word length and input power on nonlinear crosstalk induced by hybrid optical amplifiers

In this paper, the influence of the word length (WL) of a pseudo-random bit sequence (PRBS) and the input laser power on nonlinear crosstalk induced by the different hybrid optical amplifiers (HOAs) has been examined. It is found that the crosstalk is strongly dependent on the WL and very sensitive to the relative powers of the input signals at 0.2nm and 0.4nm of the channel spacing. It is shown that the proposed hybrid Raman–EDFA induces lesser crosstalk as compared to other HOAs. The performance of Raman–EDFA HOA is also investigated for 16×10Gbps dense wavelength division multiplexed (DWDM) system at 0.2nm of channel spacing.

Economic and system impact of hybrid Raman–EDFA amplification in a 40 × 40 Gbps optical transmission network with DPSK modulation

Demands of modern high-bandwidth services drive the need to constantly improve existing optical amplification technology beyond its current bounds. In this paper, we demonstrate a hybrid broadband amplification scheme which is capable of improving the system performance of a wavelength-division-multiplexed (WDM) network. We present the study of optical signals with differential-phase-shift keying (DPSK) modulation at 40Gbps and its transmission in a 50-GHz spaced, 40-channel WDM system over an 80-km link with hybrid optical amplification. A comparison of the system and cost impacts of a Raman-only amplification scheme with two hybrid Raman–erbium doped fiber amplifier schemes (Hybrids I and II) is performed. It is shown that one of the proposed hybrid schemes (Hybrid II) outperforms the other by (i) improving the tolerance to signal input power by 17dB and (ii) increasing the system reach by 55km for input signal power of 5dBm, for a bit error rate (BER) performance of 10−12.

Hybrid optical amplifiers for 64 × 10 Gb ps dense wavelength division multiplexed system

In this paper, the performance of optical/hybrid optical amplifier for 64×10Gbps dense wavelength division multiplexed system has been compared. It is observed that hybrid optical amplifier (RAMAN–EDFA) provides better results as compared to conventional amplifiers. The impact of modulation formats (NRZ, RZ and DPSK) on hybrid optical amplifier has been further investigated and it is found that 64×10, RZ is more adversely affected by nonlinearities, where as NRZ and DPSK is more affected by dispersion.

Investigation of Hybrid Optical Amplifiers for Dense Wavelength Division Multiplexed System with Reduced Spacings at Higher Bit Rates

This article proposes various combinations of optical amplifiers for a dense wavelength division multiplexed system and investigates the impact of reduced channel spacing at high bit rates in terms of quality factor, bit error rate, eye closure, and output power. It is reported that the hybrid optical amplifier (Raman–erbium-doped fiber amplifier [EDFA]) provides better results with a maximum covered single span distance (220 km) at channel spacing of 6.25 GHz. The maximum acceptable bit rate for the 12.5-GHz channel spacing dense wavelength division multiplexed system is also investigated, and the recommendation is provided that for the Raman–EDFA, Raman–EDFA–Raman, EDFA–Raman–EDFA, and EDFA–semiconductor optical amplifier–EDFA, the operating bit rate should not be greater than 20, 16, 19, and 20 Gbps, respectively.

Placement of hybrid optical amplifier in fiber optical communication systems

In this paper, we investigated the post-, pre- and symmetrical power compensation methods for a different position of hybrid optical amplifier RAMAN–EDFA in fiber link. The effect of increase in signal input power for three power compensation methods is compared in terms of bit error rate, eye closure penalty and output received power. It is found that the post power compensation method is superior to pre- and symmetrical power compensation methods. Further, the effect of variation in length of the standard single mode fiber and dispersion-compensated fiber for three power compensation configurations has also been observed. We observed that RAMAN–EDFA as post power compensation method provides least bit error rate (10−40) and high output power (12dBm) at −15dBm signal input power at fiber link.

Suppression of transient phenomena in hybrid Raman/EDF amplifier

Transient phenomena of hybrid Raman/erbium-doped fiber amplifier (EDFA) upon optical channel add-drop are investigated. The transient responses of surviving channels are resulted from the combined dynamics of Raman amplifier and EDFA. It is shown that the suggested method employing fast gain control of EDFA only can effectively suppress the transient variation of output power. The transient-suppressing hybrid Raman/EDFA is proven to be enough for wavelength-division-multiplexing networks including reconfigurable optical add-drop multiplexer and/or transparent optical cross-connect, if the optical switching speed is carefully chosen.