Study of DWDM-ROF link nonlinear effects using direct and external ODSB modulation formats

A ROF system based on 18-tuple frequency millimeter wave generation using external modulator and SOA

Research on photonic generation of quadrupling triangular-shaped waveform using external modulation

In the paper, we proposed a simple method to generate two millimeter-wave (MMW) signals for radio-over-fiber (RoF) systems. Firstly, we utilized two cascaded dual-drive Mach-Zehnder modulators (DD-MZMs), both biased at the maximum transmission bias point (MATBP), to implement frequency octupling. And then, a wavelength division multiplexing demultiplexer (WDM Demux) is followed to filter out the −4 order optical carriers of the second DD-MZM's output to enable an optical single side-band (OSSB) modulation by only modulating the baseband data onto the −4 order optical carrier. On the other hand, the +2 order optical carrier of the first DD-MZM's output is filtered out based on an optical splitter (OS) and an optical rectangle band-pass filter (ORBPF). After that, the +2 and the −4 order optical carriers are combined to be transmitted in an identical fiber path. Finally, a 45 GHz and a 60 GHz MMWs were generated simultaneously with a 7.5 GHz local oscillator (LO), by self-heterodyning these optical carriers in a photonic detector (PD). After 50 km single-mode fiber (SMF) transmission distances, the 45 GHz and the 60 GHz MMWs were maintaining good performance with clearly open eye diagrams and power penalties of 0.6 dB and 1.1 dB, respectively, at a bit-error-rate (BER) of 1×10−9.

This paper investigates bidirectional transmission using four wave mixing (FWM) for wavelength division multiplex passive optical network (WDM-PON) applications. A semiconductor optical amplifier (SOA) is considered to generate FWM. A use of FWM makes it possible to convert a downstream data wavelength to a different wavelength, which is used for upstream transmission. The wavelength generated by FWM can realize bidirectional transmission with a single fiber. We assume intensity modulation (IM) for both up- and down-transmission. Both an injection locked Fabry-Perot laser diode (FP-LD) transmitter and a transmitter with an external modulator are considered for upstream transmission. In both cases, an extinction ratio (Ex) of downstream signal light is very important for both sending and receiving properties and the Ex influences the bit error rate (BER) property. This paper clarifies the relationship between the Ex of FWM and the power penalty ΔP. This paper also clarify the Ex value of FWM as a function of input signal Ex using a model SOA theoretically. Fundamental transmission experiments, 10 Gbit/s downstream and 2.5 Gbit/ s upstream, using both types of transmitters confirmed the possibilities of the bidirectional transmission using FWM.

Optical modulation techniques which modulate parameters of lightwaves are categorized into direct modulation and external modulation. Direct modulation, which changes some physical parameters of light sources, can generate intensity modulated signals with simple configurations. Laser diodes convert electric current into optical power. The output optical signal can be modulated by the change of the electric current. However, the linearity and high-speed response are limited by a finite threshold current.

In this paper we investigate experimentally the effect of the modulation methods on the AM-WIRNA (wide bandpass filter-rectifier-narrow lowpass filter) system. We use two modulation methods: external modulation and direct modulation. Direct modulation is simpler, has a more linear response and requires smaller RF input power as compared to external modulation. >

A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an alpha -parameter that contributes to frequency chirping in the same manner as in the direct modulation of a semiconductor laser. In addition, the transmission bandwidth of a single-mode fiber system using an external modulator is discussed and compared with the results obtained utilizing direct laser modulation. >

Gain switching for the optical generation of modulated millimetre waves

Objectives: This study aims to enhance and optimize a modern communication system for high data rate transmission using Dense Wavelength Division Multiplexing (DWDM). The objectives include employing a 64-channel DWDM system, implementing different data speeds, and utilizing a dispersion compensation method. Methods: To achieve the objectives, we simulate and analyze the effects of Dispersion Compensation Fiber (DCF) in a DWDM system with 64 channels. The system employs Non-Return-to-Zero (NRZ) modulation format at varied bit rates and multiple energy levels. We propose a method for achieving data rates of 10 to 40 Gbps using NRZ modulation and Erbium-Doped Fiber Amplifier (EDFA) over a single-mode fiber transmission distance of 40 to 160 km, along with a dispersion compensation fiber of 8 to 32 km (DCF). The performance of the developed model is evaluated based on Quality Factor, Bit Error Rate (BER), Eye Height, and Threshold. These metrics are measured at two input energy levels from an optical power source, covering a communication capacity ranging from 0.625 Tbps to 2.5 Tbps. Findings: Through the simulations and analyses, we uncover the impact of dispersion and demonstrate the effectiveness of the proposed method in compensating for dispersion effects. Performance analysis of two different input transmitter power levels, -10 dBm is more efficient compared to 0 dBm input transmitter power in terms of bit error rate and quality factor. Novelty: This study presents a novel approach to improving modern communication systems by utilizing DWDM with a dispersion compensation method. The use of a 64-channel DWDM system, combined with the proposed NRZ modulation technique and dispersion compensation fiber, provides an efficient solution for achieving high data rates over long transmission distances while minimizing the effects of dispersion. The findings contribute to the advancement of communication systems for high data rate transmission. Keywords Dispersion effect, Bit Error Rate, Q-factor, Optisystem software, Erbium doped fiber amplifier

Optical fiber communication technology is beneficial to satisfy today's increasing demands for high data rates. This need for higher data rates and bandwidth has driven the fast development of fiber optic communication technologies. But at the same time, some undesirable nonlinear effects in the optical fiber medium become noticeable at high power levels. These fiber nonlinearities affect the optical fiber communication systems. The light signal in Wavelength Division Multiplexing (WDM) system can be degraded due to nonlinear impairments in the fiber. So it has become necessary to study the nonlinear effects. In this paper, nonlinear effects called Self-Phase Modulation (SPM) and Four-Wave Mixing (FWM) are observed. Factors responsible for variations in SPM and FWM effects are analyzed using OptiSystem simulation tool.

Radio over Fiber (RoF) as part of optical fiber communication could be the solution to the increasing number of demands in the success of telecommunication data processing, especially indoor where the communication traffic is higher than outdoor. An RoF network system set up is proposed for indoor application implementing for Indonesia's optical fiber communication system, which provides important benefits for the overall telecommunication system. In this network set up, DPSK digital modulation is used to modulate data in the RF signal. MZM is added as an external modulator. Random binary data is generated using PRBSs with 1 GBits/s bit rate. Various variants of 1:2, 1:4, and 1:8 power splitters are analyzed to identify the best performance of the network system. Received power, Q-Factor and Bit Error Rate are the performance parameters to determine the performance of the proposed network system. The performance parameters standards that are used is based on general telecommunication system in Indonesia with the ideal value of Q-Factor at 6, maximum BER at 10–9 and Received Power $\geq-35\mathbf{dBm}$ .

A radio over fibre (RoF) system is designed to be in an integrated fiber-wireless access network using the millimeter-wave (mm-wave) as a wireless transmission carrier. The design employs the dual-sideband optical carrier suppression (DSB-OCS) technique for mm-wave carrier generation purpose. A dual-electrode Mach-Zehnder modulator (DE-MZM) is used in this technique to generate 40 GHz carrier in order to distribute 1.25 Gbps data via direct modulation (DM) over a 20km RoF system. The link budget shows that Gigabit-per-second (GBps) wireless transmission of 1.4m distance can be achieved using direct modulation laser diode (DMLD) with the bit error rate (BER) of 10−9 and wireless transmit power of −12.38 dBm. The proposed system is able to upgrade existing passive optical network (PON) system to carry high capacity wireless signal for future high speed GBps distribution system.

It is well known that four-wave mixing (FWM) couples the longitudinal modes of a semiconductor laser.1 Such a coupling, although not commonly included in the laser rate equations, can significantly affect the noise characteristics. Both interband and intraband contributions to FWM should be considered. The interband contribution is generally believed to be negligible because of a relatively slow response time (≈1 ns) and a large mode spacing (≈100 GHz). The intraband contribution has its origin in the nonlinear gain whose response is governed by the intraband relaxation time (≈ 0.1 ps). We study the effects of such FWM by numerical simulation of the appropriately modified stochastic rate equations. The equations incorporate not only FWM but also the coupling through self- and cross-saturation.

Different types of laser source modulation techniques have been used in various applications depending on the objective. As optical systems extract the laws and the best solutions from experiments and simulations, the present study uses simulation software with different modulation types so the output signals can be compared. The modulators used are Mach-Zehnder, which is an external modulator, and electro-absorption modulator and laser rate equation modulator, which are direct modulators. All these types have an optical link multimode (MM) fiber with a photodiode in the receiver end that can be modeled. The input and output signals are analyzed using different types of modulations.

Reduction in timing jitter by chirp selection for externally modulated return to zero optical soliton pulse at 10 Gb/s