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In this paper, a novel architecture of bidirectional underwater wireless optical communication (UWOC) system has been proposed to interconnect stationary and moving underwater sensor nodes for diverse applications. To achieve the bidirectional communication, wavelength division multiplexing (WDM) and remodulation approach have been used in this work. The proposed bidirectional UWOC system works at 40 Gbps data rate for both downlink (stationary node to moving node) and uplink (moving node to stationary node). Two distinct wavelengths of 532 nm and 531 nm have been used for uplink and downlink, the main attraction of the proposed architecture is that both the laser sources are placed at the stationary node. The moving node do not have any laser source and it remodulates the signal for sending data back to the stationary node. Because of this, the moving node contains lesser components which results in cost effectiveness, low power requirement and light weight. The proposed system successfully transmits the bidirectional information at a link range of 40 m under pure sea conditions in the presence of distinctive air bubble populations. The observed bit error rate (BER) values are 1.89 × 10− 13 and 1.19 × 10− 04 for the downlink and uplink respectively at a link range of 40 m, these BER values are under the acceptable forward error correction (FEC = 2 × 10− 3) limit. The proposed bidirectional UWOC system is beneficial for the development of a high-speed last-mile underwater solution. [ABSTRACT FROM AUTHOR]

In this paper, the 50 Gbps next generation passive optical network stage 2 (50G- NGPON2) architecture is proposed via converging millimeter wave (MMWave) over fiber technology to meet the requirements of fifth generation (5G) fronthaul network such as enormous demand of high transmission rate and huge bandwidth. It uses the non-return to zero (NRZ) line code to generate pulse for 50 Gbps of data per channel, 28 GHz MMWave spectrum band over 60 km of bi-directional fiber span under the ITU-T G.9804 standardization. Two ideal erbium dopped fiber amplifiers (EDFA) with the gain of 10 dB and 5 dB respectively are used to amplify the signal on the transmitter side before transmission and receiver side after transmission. Outcomes of the proposed system demonstrate the network structure performance efficiency via Q-Factor (> 6), error rate, spectrums, and eye diagram. The variations of the Q-Factor for all optical network units (ONUs) during downstream and channels during upstream can be seen at the different fiber spans. Considering the scope of the future, in the area of digital processing, a single channel 50G-PON using 16-QAM is presented to improve the modulation and demodulation of MMWave spectrum. [ABSTRACT FROM AUTHOR]

For the first time, a novel net gain analytical model of EDFA–Raman hybrid optical amplifier (HOA) is designed and optimized the various parameters using genetic algorithm. Our method has shown to be robust in the simultaneous analysis of multiple parameters, such as Raman length, EDFA length and its pump powers, to obtained highest possible gain. The optimized HOA is further investigated and characterized on system level in the scenario of 100×10 Gbps dense wavelength division multiplexed (DWDM) system with 25 GHz interval. With an optimized HOA, a flat gain of >18 dB is obtained from frequency region 187 to 189.5 THz with a gain variation of less than 1.35 dB without using any gain flattened technique. The obtained noise figure is also the lowest value (<2 dB/channel) ever reported for proposed hybrid optical amplifier at reduced channel spacing with acceptable bit error rate. [ABSTRACT FROM AUTHOR]

We proposed a bandwidth efficient wavelength division multiplexed-passive optical network (WDM-PON) to simultaneously transmit 60 Gb/s unicast and 10 Gb/s multicast services with 10 Gb/s upstream. The differential phase shift keying (DPSK) multicast signal is superimposed onto multiplexed non-return to zero/polarization shift keying (NRZ/PolSK) orthogonal modulated data signals. Upstream amplitude shift keying (ASK) signals formed without use of any additional light source and superimposed onto received unicast NRZ/PolSK signal before being transmitted back to optical line terminal (OLT). We also investigated the proposed WDM-PON system for variable optical input power, transmission distance of single mode fiber in multicast enable and disable mode. The measured Quality factor for all unicast and multicast signal is in acceptable range (>6). The original contribution of this paper is to propose a bandwidth efficient WDM-PON system that could be projected even in high speed scenario at reduced channel spacing and expected to be more technical viable due to use of optical orthogonal modulation formats. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated wavelength division multiplexed (WDM) hybrid (ring-tree-star) topology. Eight optical add/drop multiplexers (OADMs) are used to make ring structure. The single mode fiber and dispersion compensating fiber and semiconductor optical amplifier (SOA) are employed between each OADM to achieve a maximum. To increase the number of users each OADM node of ring network is connected to star and tree network topology which can accommodate more than 2048 users. Various system parameters (for different channel spacing, different input power signal, different data rates and the fiber length) are varied to investigate the system performance in the term of BER and Q factor. [ABSTRACT FROM AUTHOR]

We propose a new optical data format based on simultaneously modulating nonreturn-to-zero and polarization-shift-keying for high-speed applications by means of efficient utilization of bandwidth. To the best of our knowledge, this article reports on the first investigation of a Raman erbium-doped fiber amplifier hybrid optical amplifier using a hybrid/orthogonal modulation technique in the scenario of 8- and 20-channel dense wavelength division multiplexed systems with high-data rates at 0.2 and 0.8 nm channel spacing, respectively. The results show that the proposed modulation format offers significant advantages in offering high-spectral efficiency values with acceptable quality factors and bit error rates. [ABSTRACT FROM AUTHOR]

For the first time, a novel flat-gain optical amplifier is proposed using a hybrid configuration with an Er-Yb co-doped waveguide amplifier (EYDWA) and a semiconductor optical amplifier (SOA) for 100 × 10-Gb/s dense wavelength division multiplexed system at 0.2 nm interval. With an EYDWA-SOA hybrid amplifier, a flat gain of is obtained across the effective bandwidth with a gain variation of the order of 0.75 dB without using any gain clamping techniques. It is observed that when the proposed hybrid amplifier is used as a booster for hybrid distributed Raman amplifier and erbium doped fiber amplifier, the gain variation is reduced from 2.01 to ~ 1.15 dB efficiently with acceptable bit error rate. [ABSTRACT FROM PUBLISHER]

We present a simple genetic algorithm implemented to perform multiparameter optimization of a Raman fiber amplifier for a 100-channel L-band dense wavelength division multiplexed system at a 25-GHz interval. The system is investigated for various cases with fixed pump frequency leading to 202.2-THz pump as the best choice with average gain above 19.5 dB. There is evidence to show that a single counterpropagating pump optimized to 588.2-mW power level and optimum Raman fiber length of 38.8 km presents a small gain variation (<2 dB) over an effective bandwidth covering 187 to 189.475 THz. The optimized configuration enabled an adequate system performance in terms of acceptable Q-factor (17 dB) and bit error rate (5.60 x 10-13). [ABSTRACT FROM AUTHOR]

Highlights: [•] The influence of crosstalk induced by hybrid optical amplifiers has been examined. [•] It is observed that as the input power increases the crosstalk will also increase. [•] It is recommended that R–E is the best combination as compared to other HOA. [•] The investigation of crosstalk has also been done in 16 channel DWDM system. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, four modulation formats including nonreturn-to-zero (NRZ), nonreturn-to-zero raised cosine (NRZ-RC), return-to-zero (RZ), return-to-zero raised cosine (RZ-RC) DWDM system with different hybrid optical amplifiers are introduced. We show that NRZ-DPSK and RZ-DPSK degrade the performance when Raman amplifier is considered. The obtained results reported that RZ and RZ-RC DWDM system with Raman-EDFA provide better results and cover 1512 and 1260km of transmission distance, respectively, with acceptable quality factor (>15dB) and bit error rate (<10−9). Further, it is also confirmed that using the hybrid optical amplifiers is a best alternative to increase the span distance. [Copyright &y& Elsevier]

Abstract: In this paper, we investigate pre-, post-, symmetrical dispersion and power compensation in parallel for 96 channels×10Gbps non-return to zero DWDM system using pumped dispersion compensating fiber (PDCF) and pumped single mode fiber (PSMF). The results of three compensation methods have been compared in the term of bit error rate, eye closure penalty and Quality factor and it is found that both post-, and symmetrical compensation methods are provide better results for short haul communication but for long haul communication post-compensation method is the best alternative among other. The impact of bit error rate and eye closure penalty is also observed for large transmission distances and cover 420km using post-compensation method with acceptable bit error rate (2.3×10−10) and eye closure (1.73dB). [Copyright &y& Elsevier]

Abstract: In this paper 10Gbps WDM systems at 16, 32 and 64 channels have been investigated with EDFA, RAMAN and SOA amplifiers individually and the performance has been compared on the basis of transmission distance and dispersion with and without nonlinearities. It is demonstrated that when the dispersion is 2ps/nm/km and the number of channels are less, then SOA provide better results because as we increases the number of channels, the gain saturation problem arises due to cross gain modulation, the cross phase modulation and four wave mixing. When dispersion is increased from 2 to 10ps/nm/km, EDFA provides better results than SOA in the term of BER and output power, but it shows non-uniform gain spectrum. We also observed that RAMAN amplifier provides better results for L band amplification and gain flatting issue because it can substantially reduce the impact of fiber nonlinearity. [Copyright &y& Elsevier]

Abstract: In this paper, we investigated the performance of multi terabits DWDM system consisting of hybrid optical amplifier RAMAN-EDFA for different data format such as non-return to zero (NRZ), return to zero (RZ) and differential phase shift keying (DPSK). We find that in 64×10 and 96×10Gbps, RZ is more adversely affected by nonlinearities, where as NRZ and DPSK is more affected by dispersion. We further show that RZ provide good quality factor (13.88dB and 15.93dB for 64 and 96 channels), less eye closure (2.609dB and 3.191dB for 64 and 96 channels) and acceptable bit error rate (3.89×108 and 1.24×109 for 64 and 96 channels) at the respective distance as compare to other existing modulation format. We further investigated the maximum single span distance covered by using existing data formats. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the wavelength division multiplexed (WDM) system using ring network topology. This network is used to increase the capacity with eight optical add/drop multiplexers (OADMs) by using dispersion compensating fiber and semiconductor optical amplifier (SOA) to achieve a distance up to 1600 km. It is observed that network shows the acceptable results at 15 Gbps data rate with 100 GHz channel spacing. The OADM nodes are also varied to investigate the network performance in the term of BER and Q -factor. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Summary: In this paper, we have proposed a high‐performance transmission system of 32 channels based on dense wavelength division multiplexing (DWDM) through an optical fiber link consisting of 110 km per span. To check the influence of nonlinear effects, we have considered phase modulation (SPM), cross‐phase modulation (XPM), four‐wave mixing (FWM), stimulated Raman scattering (SRS), and self‐steepening (SS) which limits the performance of optical communication systems. In the proposed system, each channel is modulated at 200 Gbps of dual‐polarization quadrature phase shift keying (DP‐QPSK) format, with a 50‐GHz grid yield whole data rate of 6.4 Tbps. The results have proved that the nonlinear phenomena degrade the performance of proposed optical fiber communication systems, and XPM has the most dominant effect, followed by SS, SRS, and SPM. The simulation was carried out with Optisystem 14 which is powerful software for modeling and simulation of optical fiber transmission. [ABSTRACT FROM AUTHOR]

• A novel remote node design has been presented with fiber fault protection for ring topology NG-PON2. • The presented NG-PON2 architecture is based on single fiber ring topology. • The proposed remote nodes are able to communicate in both clockwise and anticlockwise directions. • In case of fiber fault the remote nodes can change the direction of communication and service disruption can be avoided. The service disruptions in passive optical networks (PONs) due to fiber or node failure is an important issue. In the conventional star topology time and wavelength division multiplexing (TWDM) based next generation passive optical network stage 2 (NG-PON2), there is no provision to restore the service if the fiber between remote node (RN) and optical network unit (ONU) fails. In this paper, we proposed a novel entirely passive node design for ring based NG-PON2 which provides fiber fault protection against any fiber break between RNs. The working of the proposed node is verified by simulating normal conditions and fault conditions. It is observed that in the case of fiber failure, the affected ONUs can still communicate with the optical line terminal (OLT). The performance of the system has been analyzed in terms of bit error rate (BER), and the BER <10−9 confirms the correct working of the system. [ABSTRACT FROM AUTHOR]