Electrode Mach-Zehnder Modulator Research Articles

Intensity and Phase Modulators at 1.55 μm in GaAs/AlGaAs Layers Directly Grown on Silicon

We report for the first-time electro-optic phase and amplitude modulators in GaAs/AlGaAs epitaxial layers grown on misaligned silicon substrates containing germanium buffer layers. Epilayer has a npin doping profile and is equivalent to a pin diode. The 4-mm long electrode Mach–Zehnder modulators have 7.4- and 3.6-V Vπ under single-arm and push–pull drive conditions corresponding to 1.5 ± 0.1 V-cm modulation efficiency. Data on 7-mm long electrode Fabry–Perot phase modulators indicate 2.3-V Mach–Zehnder modulators are possible. These data also indicate less than 1-dB/cm on-chip propagation loss under 5-V reverse bias.

An 80 Gbps multi-band access radio over fiber link with single side band optical millimeter-wave dispersion-tolerant transmission without FBG and optical filter

We are presenting a new low-cost Single Sideband (SSB) modulated Radio-over Fiber (RoF) communication system for millimeter (mm)-wave multiband wireless communication at the frequencies of 40 GHz, 80 GHz and 120 GHz. Its principle lies in the Carrier Suppressed modulation through a nested dual electrode Mach–Zehnder Modulator (MZM) and product modulator based baseband signal decomposition. In this novel method, the optical signal is decomposed into different SSB signals using a power splitter and product modulators at the base station. This proposed method uses a different technique for a baseband signal decomposition from the existing method. The proposed signal decomposition technique has reduced the nonlinearities due to the FBGs. The proposed method is compared with the existing method in terms of BER, data rate and OSNR. The simulation results disclose that our proposed scheme outperforms the existing methods at a higher data rate of 80 Gbps with a minimum BER and privileged Q factor.

Low Switching Voltage Mach–Zehnder Modulator Monolithically Integrated With DFB Laser for Data Transmission up to 107.4 Gb/s

We present a transmitter optical subassembly consisting of an InP-based travelling wave electrode Mach–Zehnder modulator monolithically integrated with a distributed feedback laser. At 56-Gb/s non-return-to-zero ON/OFF keying (NRZ-OOK), we achieve 3.5-km transmission before breaking the hard decision forward error correction threshold (3.8 ×10−3). 9-km transmission is achieved at 71.6-Gb/s 4-pulse–amplitude modulation (PAM4) and 5 km at 107.4 Gb/s PAM8. The modulation voltage is between 1.5 and 2 V, leading to overall power consumption of 171 mW for the NRZ-OOK case and 206 mW at PAM4 and PAM8.

Distributed electrode Mach-Zehnder modulator with double-pass phase shifters and integrated inductors.

A novel high-speed Mach-Zehnder modulator (MZM) fully integrated into a 90 nm CMOS process is presented. The MZM features 'double-pass' optical phase shifter segments, and the first use of integrated inductors in a 'velocity-matched' distributed-electrode configuration.

Wideband direction finding using a photonic robust symmetrical number system technique

Dual electrode Mach–Zehnder modulators (DE-MZMs) are used to conduct phase detection for direct wideband direction finding (DF) of microwave signals. It is demonstrated theoretically and through simulation and experimentation that the normalized magnitude of the output signal phase detector circuit is equal to |sin(ψ/2)|, where ψ is the phase difference between the plane waves arriving at the reference and measurement antennas of a linear DF array. A four-element wideband photonic DF system with robust symmetrical number system preprocessing is presented. Simulation and experimental testing results are provided to demonstrate the theoretical concept. The results demonstrate a direct DF receiver using DE-MZMs that achieves fine angular resolution using a much smaller array size than is typically required for linear arrays employing super-resolution signal processing techniques.

Framework for optical millimetre‐wave generation based on tandem single side‐band modulation

A novel scheme for optical millimetre-wave (mm-wave) generation based on tandem sub-carrier multiplexing in hybrid communication systems is suggested. The method is analysed mathematically for optimum settings. The tandem single side-band (TSSB) method is tolerant to fibre chromatic dispersion. However, the TSSB technique is prone to critical interference of unwanted harmonics which may result in poor data transmission bit error rate (BER). Based on the proposed mathematical derivation for TSSB modulation, a framework is provided to enhance the mm-wave generation system performance. Up to 2 Gb/s data transmission over multiple 60 GHz sub-bands is considered. The model includes a single-mode fibre with chromatic dispersion factor of 16 ps/(nm km). Two cascaded dual electrode Mach–Zehnder modulators are used to generate TSSB 60 GHz sub-bands. Three oscillators are required to generate two tandem mm-wave signals. A proper selection of these three frequencies is vital to guarantee a successful data transmission. Mathematical analysis is carried out to verify the proposed scheme and a summary of appropriate frequency sets is presented and discussed. The BER curves are obtained. The results verify that the TSSB-based mm-wave generation framework proposed in this study guarantees data transmission with an acceptable BER.

On the carrier generation and HD signal transmission using the millimeter-wave radio over fiber system

The dual sideband optical carrier suppression (DSB-OCS) technique is employed in the optical carrier generation for 40GHz radio over fiber (ROF) system. A dual electrode Mach-Zehnder modulator (DE-MZM) with the minimum transmission bias (MiTB) technique is employed to build the system. The results show that, a 40GHz carrier is successfully generated with the amplitude up to −29dBm and signal to noise ratio (SNR) of 35dB and a high definition (HD) signal is successfully transmitted using the system. Finally, the bit error rate (BER) measurement is carried out for the system with 1.25Gbps OOK signal showing an error free 40GHz ROF system with almost no penalty between the back to back and 20km fiber for a BER of 10−9.

A tunable optoelectronic oscillator based on a tunable microwave attenuator

A novel realization of a wideband tunable optoelectronic oscillator (OEO) based on dual-port electrode Mach–Zehnder modulator (DMZM), a tunable microwave attenuator (TMA), and a chirped fiber Bragg grating (CFBG) is proposed and demonstrated. By simply adjusting the power ratio between the two arms of DMZM, the chirp of the DMZM will be tuned, and the center frequency of the microwave photonic filter will be tuned. When the OEO loop in the proposed system is closed, the output frequency of OEO is determined by the microwave photonic filter, and a high spectral purity microwave signal with a tunable frequency from 5.8 to 11GHz is generated. The single sideband (SSB) phase noise of the generated signal could reach −107.4dBc/Hz at an offset frequency of 10kHz.

Impact of the Modulation Chirp of a DEMZM on the Transmission of Signals Based on OFDM

We investigate the transmission performance of an optical signal composed by a custom orthogonal frequency-division multiplexing (OFDM) gigabit ethernet (GbE) signal, a long-term evolution (LTE) signal, and an OFDM ultrawideband (OFDM-UWB) signal, when chirp is introduced in the intensity modulation based on a dual electrode Mach-Zehnder modulator. The results show that, when the optical signal is generated with controlled negative chirp, it is possible to reduce the optical signal-to-noise (OSNR) penalty after transmission through a long reach fiber-to-the-home network by approximately 5, 1.5, and 0.5 dB, for the OFDM-UWB, LTE, and OFDM-GbE signals, respectively. Furthermore, the results show negative OSNR penalty for OFDM-UWB and LTE signals after transmission, for specific distances.

Performance Analysis of a Photonic-Assisted Periodic Triangular-Shaped Pulses Generator

We propose and analyze a photonic-assisted periodic triangular-shaped pulses generator, in which a continuous wave (CW) laser is connected to a dual electrode Mach-Zehnder modulator (De-MZM), and then the De-MZM is connected with a normal dispersion fiber or element. A radio frequency (RF) sinusoid directly drives the De-MZM to obtain optical subcarrier modulation with optical carrier suppression. By carefully setting the physical parameters, the generated harmonics of optical intensity can be corresponding to the Fourier components of typical periodic triangular pulses. Numerical simulations reveal that modulation index must be set to 2.305 and bias voltage drift must be within a range from from the minimum transmission of the De-MZM. In addition, the dispersion must be set correctly to suppress the primary distortion of 4th order harmonics.

Error Vector Magnitude Analysis of Radio-over-fiber Systems Based on Single Side Band Modulation

In order to meet the increasing demand for wireless connectivity and large coverage, radio-over-fiber (RoF) infrastructure has been suggested as a cost-effective solution for the provisioning of bandwidth in small cell size. In the present work, performance analysis has been done for radio over systems based on optical single side band technique. Error vector magnitude (EVM) has also been quantified for RoF link in the presence of dispersion and phase noise incorporating dual electrode Mach-Zehnder modulator (DE-MZM). It is found that the laser phase noise is dominant over long distances.

Analysis of frequency quadrupling using a single Mach-Zehnder modulator for millimeter-wave generation and distribution over fiber systems

We comprehensively investigate three modulation techniques for the generation of millimeter-wave (mm-wave) using optical frequency quadrupling with a dual???electrode Mach-Zehnder modulator (MZM), i.e. Technique-A, Technique-B and Technique-C. For Technique-A, an RF signal drives the two electrodes of the MZM with maximum transmission bias, and this MZM is used for both the mm-wave generation and signal modulation. Technique-B is the same as Technique-A, but 180(0) phase shift between the two electrodes is applied. Technique-C is the same as Technique-B, but the MZM is only used for the mm-wave generation without signal modulation. It is found that Technique-B and Technique-C are better for frequency quadrupling than frequency doubling, tripling and sextupling. Both theoretical analysis and simulation show that the generated mm-wave suffers from constructive/destructive interaction due to fiber chromatic dispersion in Technique-A. However, the generated mm-wave is almost robust to fiber chromatic dispersion in Technique-B and Technique- C. It is found that Technique-C is the best in the quality of the generated mm-wave, especially when poor optical filtering is used. In addition, we develop a theory for calculation of Q-factor for mm-wave generation using the three modulation techniques. We consider an RF at 7.5 GHz and obtain an mm-wave at 30 GHz as an example, i.e. a frequency quadrupler. We evaluate the generation and distribution in terms of system Q-factor. The impact of RF modulation index, chromatic dispersion, MZM extinction ratio and optical filtering on Q-factor are investigated.

Prechirped duobinary modulation

The proposed modulation scheme enables us to combine the advantages of the duobinary modulation, i.e., reduced transmission bandwidth compared to traditional intensity modulation, together with the advantages of prechirped modulation. Below, a theoretical investigation is presented where four different methods of modulating a double electrode Mach-Zehnder modulator is compared. It will be shown that the proposed prechirped duobinary modulation scheme will have the best performance in terms of power penalty.

Novel automatic bias voltage control for travelling-wave electrode optical modulators

A novel method to control the bias voltage of LiNbO/sub 3/ travelling-wave electrode Mach-Zehnder modulators for multigigabit per second NRZ signals is proposed. This method uses the difference in modulator bandwidth for copropagating and counterpropagating signals against the travelling modulation field. This method successfully controls a modulator without distorting the output optical waveform. >