The demand for high speed in wireless communication is a big concern since the number of connections is increasing. The employment of higher carrier is strongly recommended and millimeter wave (mm-wave) frequency are necessary in the future. In this paper, we propose the generation and the transmission of multiband signal for millimeter-wave Radio over Fiber (RoF) system using the full spectrum of 200 -300GHz for downlink transmission of 10 Gb/s On off Keying (OOK) and 40 Gb/s Differential Quadrature Phase Shift Keying (DQPSK). An optimized Optical Flat Comb Source (OFCS) based on dual-arm Mach-Zehnder Modulator (MZM) is employed in order to generate 5 carriers with 25 GHz spacing and centered around 250 GHz. For 10 Gb/s OOK and 40 Gb/s DQPSK, the system performances are evaluated by measuring the Bit Error Rate (BER). In addition, we have studied the Error Vector Magnitude (EVM) for 40 Gb/s DQSK system.The obtained results have been done for single and multiband channels. At first, we have explored the effect of the optical fiber in the performance of our system. The optical fiber is inserted after each modulatorand after the local oscillator (LO) for path compensation.The optical delay line has an important role in reducing interference between channels. Furthermore, we discuss the performance of the system in back to back transmission in different cases such as without wireless link and with wireless link. Finally, we have studied the wireless link distances for acceptable BER below Forward Error Correction (FEC) limit BER 3.8x10-3 and EVM for each modulation format. The transmission link length is about 2 m. The generated signal is used for short range indoor wireless systems.
KEYWORDS: Modulation, Signal to noise ratio, Receivers, Signal generators, Single mode fibers, Phase shift keying, Radio optics, Wavelength division multiplexing, Oscillators, Distributed computing
Due to the growth of the number of communication devices over the last decades, the millimeter wave (mm-wave) band has been strong interest. In fact, this band offers a massive bandwidth and highest speed. However, in order to obtain the highest receiver sensitivity, it's necessary to generate the millimeter wave signals with low phase noise. In this paper, we propose the photonic generation of mm-wave signals with three methods. The generation is based on an optical frequency comb source (OFCS) from which five carriers are selected for 40 Gb/s Differential Quadrature Phase Shift Keying (DQPSK) modulation. At the level of the photo-detector, the optical local oscillator (LO) beats the mm-wave modulated signal. In the first case, the optical LO is distributed and emitted from an independent laser. In the second case, the optical LO which is a comb line is lumped. Finally, the optical LO is in an Optical Phase Locked Loop (OPLL) with the OFCS. Furthermore, we compare the performance of the 40 Gb/s DQPSK mm-wave generation and transmission system in the band of 200 - 300 GHz. We discuss their back-to-back (b-to-b) and over 10 km Single Mode Fiber (SMF) in term of Bit Error Rate (BER), Quality factor (Q factor), Signal to Noise Ratio (SNR) for single channel and for multiband channels in the band of 200 - 300 GHz. The system using the phase locked LO source has the high receiver sensitivity since the OPLL assured his phase stabilization. The 250 GHz channel has the best results for single band and multiband generation.
There is a need, for high speed optical communication networks, in the monitoring process, to determine the modulation format type of a received signal. In this paper, we present a new achievement of modulation format recognition technique, where we proposed the use of wavelet transform of the detected signal in conjunction with the artificial neural network (ANN) algorithm. Besides, wavelet transform is one of the most popular candidates of the time-frequency transformations, where the wavelets are generated from a basic wavelet function by dilations and translations. We proved that this technique is capable of recognizing the multi-carriers modulation scheme with high accuracy under different transmission impairments such as chromatic dispersion (CD), differential group delay (DGD) and accumulated amplified spontaneous emission (ASE) noise with different ranges. Both the theoretical analysis and the simulation results showed that the wavelet transform not only can be used for modulation identification of optical communication signals, but also has a better classification accuracies under appropriate OSNR (optical signal-to-noise ratio) values.
KEYWORDS: Radio over Fiber, Extremely high frequency, Radio optics, Hybrid fiber radio, Modulators, Picosecond phenomena, Telecommunications, Transceivers, Communication engineering, Heterodyning
In this paper, we propose a flexible monocycle generator that is based on multi-tonal excitation of a dual-arm MZM. The proposed generator permits the generation of different waveforms, such as Gaussian, first order Gaussian derivative, sinusoidal, cosine and sinc pulses. We exploit the proposed generator in order to generate the International Telecommunication Union-Radiocommunication( ITU-R) recommended channelization which contains four carrier frequencies, spaced by 2.16 GHz (58.32 GHz, 60.48 GHz, 62.64 GHz and 64.80 GHz). This millimeter waves (mmwaves) have attracted a great deal of attention in the Radio over Fiber (RoF) systems. The main challenge of the RoF system is to provide higher bands and increase significantly data rate with using millimeter-wave (mm-wave) band.
A new technique for Automatic Modulation Format Recognition (AMFR) in next generation optical communication networks is presented. This technique uses the Artificial Neural Network (ANN) in conjunction with the features of Linear Optical Sampling (LOS) of the detected signal at high bit rates using direct detection or coherent detection. The use of LOS method for this purpose mainly driven by the increase of bit rates which enables the measurement of eye diagrams. The efficiency of this technique is demonstrated under different transmission impairments such as chromatic dispersion (CD) in the range of -500 to 500 ps/nm, differential group delay (DGD) in the range of 0-15 ps and the optical signal tonoise ratio (OSNR) in the range of 10-30 dB. The results of numerical simulation for various modulation formats demonstrate successful recognition from a known bit rates with a higher estimation accuracy, which exceeds 99.8%.
KEYWORDS: Receivers, Modulation, Complex systems, Polarization, Signal detection, Signal to noise ratio, Channel projecting optics, Frequency division multiplexing, Device simulation, Single mode fibers
In this paper, we implement an Optical Flat Comb Source generating a coherent super-channel operating at 1 Tbps using Wavelength Division Multiplexing-Nyquist (WDM-Nyquist) and Coherent Optical-Orthogonal Frequency Division Multiplexing (CO-OFDM) approaches with 12.5 GHz channel spacing. We evaluate through simulation the performance of the two techniques for generating Dual Polarization Quadrature-Amplitude Modulation based on 16 (DP-16QAM). We first study the robustness of CO-OFDM system to the receiver constraints such as Analog-to-Digital Converters (ADCs) speed and the receiver bandwidth in Back-to-Back link (Optical Signal-to- Noise Ratio (OSNR)) and over longhaul dispersion compensated links using Standard Single Mode Fiber (SSMF). We find that CO-OFDM requires 6 Samples per Symbol (SpS) with a large receiver bandwidth (2.25× Baud rate) to achieve the same performance of WDM-Nyquist system in terms of SNR. However, the CO-OFDM system needs more than 6 SpS to achieve the same distances as WDM-Nyquist. We also study the impact of the input power level in terms of OSNR for CO-OFDM and WDM-Nyquist systems in order to evaluate the robustness of both systems to the nonlinear effects.
KEYWORDS: Modulation, Orthogonal frequency division multiplexing, Optical amplifiers, Receivers, Digital signal processing, Raman spectroscopy, Optical filters, Linear filtering, Signal detection, Solids
In this paper, we implement an Optical Flat Comb Source generating a coherent super-channel operating at 1 Tbps using WDM-Nyquist and OFDM approaches with new flex-grid channel spacing. The new flex-grid defines WDM channel spacing having a multiple of 12.5 GHz. We compare through simulation the performance of two techniques for generating Dual Polarization-Quadrature Amplitude Modulation based on 16 (DP-16QAM), 64 (DP-64QAM) and 128 (DP-128QAM). We first study the performance of WDM-Nyquist and OFDM super-channels implementing DP- 16QAM, DP-64QAM and DP-128QAM in back-to-back scenarios in terms of receiver sensitivity and Optical Signal-to- Noise Ratio (OSNR) requirement with 12.5 GHz flex-grid spacing. We find that DP-16QAM has the best receiver sensitivity and the lower OSNR penalty compared to the other modulation formats in WDM-Nyquist system. With DP- 128QAM sensitivity as reference, we can observe a benefit of 10 dB for DP-16QAM with a BER equal to 3.8 10-3. In addition, we can observe a benefit of 12.4 dB in OSNR for DP-16QAM compared to DP-128QAM for a BER equal to 3.8 10-3. Also, we study the impact of the optical and electrical shaping filters. Finally, we investigate the performance of WDM-Nyquist and OFDM terabit system with 12.5 GHz flex-grid spacing over long-haul dispersion compensated links using Standard Single Mode Fiber (SSMF). We find that DP-16QAM is the suitable modulation format in dispersion compensated WDM-Nyquist systems using SSMF fiber. In addition, we prove that the use of Raman amplification improve the maximum reach of the super-channel by increasing the span distance between the amplifier module. Indeed, using the Raman amplification the maximum reach increase from 812 km to 955 km in a WDM-Nyquist system based on DP-16QAM with 12.5 GHz flex-grid spacing.
In this paper, we implement a WDM-Nyquist transmission system with 12.5 GHz channel spacing generated through an Optical Flat Comb Source (OFCS). Each channel could carry one of four different modulation format as Polarization Multiplexing-Quadrature Phase Shift Keying (POLMUX-QPSK), Polarization Multiplexing-Differential Quadrature Phase Shift Keying (POLMUX-DQPSK), Polarization Multiplexing-Quadrature Amplitude Modulation based on 16 (POLMUX-16QAM) and 64 (POLMUX-64QAM) with Return-to-Zero (RZ) pulse carving and 33% duty cycle. Numerical simulations of 1 Tbit/s superchannel have been carried out, in order to evaluate the performances of the different modulation format using appropriate metrics. We discuss their back-to-back receiver sensitivity and the required Optical-to-Noise Signal Ratio (OSNR) for 3.8•10-3 and 10-9 Bit Error Rate (BER). We find that POLMUXQPSK has the best receiver sensitivity and the lower OSNR penalty compared to the other modulation formats. With POLMUX-QPSK sensitivity as reference, we can observe a power penalty of 13.4 dB (for a BER equal to 3.8•10-3) for POLMUX-64QAM. In addition, we can observe an OSNR penalty of 21 dB in OSNR for POLMUX-64QAM compared to POLMUX-QPSK modulation format for a BER equal to 3.8•10-3. However, it is important to mention that POLMUX- 64QAM presents higher Spectral Efficiency (SE). We study also the robustness of these four optical modulation formats for transmission of 1 Tbit/s in dispersion compensated WDM-Nyquist systems using two kinds of transmission fibers: SMF (Single Mode Fiber) and NZDSF (Non-Zero Dispersion Shifted Fiber). We find that POLMUX-QPSK is the suitable modulation format in dispersion compensated WDM-Nyquist systems using NZDSF fiber. We simulate the nonlinear effect tolerance by considering self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) for the different modulation format. We observe that POLMUX-QPSK has the best robustness against the cited nonlinear fiber effects in NZDSF fiber.
In this paper, we compare the performance of Polarization Multiplexing-Differential Quadrature Phase Shift Keying
(POLMUX-DQPSK) and Dual Carrier-Differential Quadrature Phase Shift Keying (DC-DQPSK) with RZ (Return-to-
Zero) carving and duty cycle of 33% in 100 Gb/s transmission systems. These formats appear to be the most promising
technology for long-haul with coherent detection. POLMUX-DQPSK use the polarization dimension of the optical signal
to transmit the information. DC-DQPSK uses two wavelengths to transmit the information. We discuss their back-toback
receiver sensitivity and required Optical-to-Noise Signal Ratio (OSNR) for a Bit Error Rate (BER) equal to 10-9.
We find that 33RZ-POLMUX-DQPSK has the best receiver sensitivity and lower OSNR penalty compared to 33RZ-DCDQPSK. For 33RZ-POLMUX-DQPSK sensitivity as reference, we can observe a benefit of 1.5 dB for 33RZ-DCDQPSK.
Also, we can observe a benefit of 2.3 dB in OSNR for 33RZ-POLMUX-DQPSK compared to 33RZ-DCDQPSK.
We study the robustness of these two optical modulation formats for transmission of 1.6 Tb/s (16×100 Gb/s)
over 1200 km in dispersion compensated Wavelength Division Multiplexing (WDM) systems with 100 GHz channel
spacing using two types of fibers Standard Single Mode Fiber (SSMF) and Non-Zero Dispersion Shifted Fiber (NZDSF).
We find that 33RZ-DC-DQPSK is a suitable modulation formats in dispersion compensated WDM systems with 100
Gb/s channel spacing using NZDSF fiber. We simulate the nonlinear tolerance of optical 33RZ-POLMUX-DQPSK and
33RZ-DC-DQPSK formats. 33RZ-DC-DQPSK modulation format has the best robustness against the nonlinear fiber
effects in NZDSF fiber.
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