Optical Single Sideband Modulator Without Second-Order Sidebands

In this paper, we investigate the optical power fluctuation of the output in optical comb generator using an optical single sideband (SSB) modulator with a fiber loop. This fluctuation is caused by undesired sidebands of the SSB modulator. We show that the fluctuation can be suppressed by stabilizing the fiber loop length. In experiment, the averaged peak-to-peak power fluctuation of 23 comb outputs was suppressed from 0.86 dB to 0.13 dB.

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.

We propose and demonstrate an optical single sideband (OSSB) modulation approach with continuously tunable optical carrier-to-sideband ratio (OCSR) theoretically and experimentally. In the proposal, one dual-parallel Mach-Zehnder modulator (DP-MZM) acts as a key component. By properly setting the modulator, three separate sub-modulators inside the DP-MZM can be used to realize the OSSB modulation, optical carrier phase-shift, and lightwave interference. By adjusting the bias voltage of one sub-modulator, the OCSR can be tuned continuously. In the experiment, the tuning range of OCSR is found to be between-20.8 dB and 23.5 dB at modulation index m=0.2. We also analyze the relationship between the OCSR and RF power after detection. It is found that with properly adjusting the OCSR, the receiver sensitivity can be greatly improved.

As a promising solution for short-to-medium transmission systems, direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) or discrete multi-tone (DMT) has been intensively investigated in last decade. Benefitting from the advantages of peak-to-average power (PAPR) reduction and signal-to-noise ratio (SNR) equalization, precoding techniques are widely applied to enhance the performance of DDO-OFDM systems. However, the conventional method of partitioning precoding sets limits the ability of precoding schemes to optimize the SNR variation and the allocation of modulation formats. Thus, the precoding transmission systems are hard to reach the capacity that traditional bit-power loading (BPL) techniques, like the Levin-Campello (LC) algorithm, can achieve. In this paper, we investigate the principle of SNR variation for precoded DDO-OFDM systems and theoretically demonstrate that the SNR equalization effect of precoding techniques is actually determined by the noise equalization process. Based on this fact, we propose an adaptively partitioned precoding (APP) algorithm to unlock the ability to control the SNR of each subcarrier. As demonstrated by the simulation and experimental results, the proposed APP algorithm achieves the transmission capacity as high as the LC algorithm and has nearly 1 dB PAPR reduction. Besides, the look-up table (LUT) operation ensures low complexity of the proposed APP algorithm compared with LC algorithm. To avoid severe chromatic dispersion (CD) induced spectral fading, single sideband (SSB) modulation is also implemented. We find that SSB modulation can reach the capacity of double sideband (DSB) modulation in optical back-to-back (OB2B) configuration by optimizing the modulation index. Therefore, the APP based SSB-DDO-OFDM scheme can sufficiently enhance the performance of cost-sensitive short-to-medium reach optical fiber communication systems.

Comparing with the conventional double-sideband (DSB) modulation in communication system, single-sideband (SSB) modulation only demands half bandwidth of DSB in transmission. Two common ways are employed to implement SSB modulation by using optical filter (OF) or electrical 90° phase shift, respectively. However, the bandwidth of above methods is limited by characteristics of current OF and electrical phase shift. To overcome this problem, an ultra-wideband microwave photonic link based on SSB modulation is proposed and demonstrated. The radio frequency (RF) signal modulates a single-drive dual-parallel Mach-Zehnder modulator, and the SSB modulation is realized by combining an electrical 90° hybrid coupler and an optical bandpass filter. The experimental results indicate that the system can achieve SSB modulation for RF signal from 2 to 40 GHz. The proposed microwave photonic link provides an ultra-wideband approach based on SSB modulation for radio-over-fiber system.

A microwave frequency shift keying optoelectronic oscillator (FSK-OEO) based on an optical single-sideband (OSSB) modulator is proposed and experimentally demonstrated. In the proposed FSK-OEO, a dual-drive Mach-Zehnder modulator (DDMZM) is employed to implement the optical single sideband modulation through the 90° phase shift method. By appropriately setting the amplitude of the coding signal applied to the DC port of the DMZM, a FSK microwave signal is generated. In the experiment, 9.995/10.004 GHz and 10.371/11.014 GHz microwave FSK signals were successfully generated by using the proposed OEO scheme. This scheme can generate high-frequency and low-phase-noise FSK signals without relying on high-frequency signal sources. Additionally, the pulse compression performance of the generated signals was also demonstrated.

Using a hyperfine blocking filter based on a virtually imaged phased-array as the spectral disperser, we present a novel scheme of optical carrier-suppressed single sideband (SSB) modulation. Our experiments demonstrate sideband suppression of /spl sim/28 dB at only a 2.9-GHz offset for single subcarrier amplitude modulated at 622 Mb/s. Furthermore, the hyperfine blocking filter can be tuned for simultaneous optical SSB and strong carrier suppression to /spl sim/30 dB lower in optical power than the unsuppressed sideband.

Real-valued neural network nonlinear equalization for complex-valued signals combined with single sideband (SSB) modulation is proposed to be a promising scheme for long-reach passive optical networks (LR-PONs). With the assist of neural network equalizer (NNE), fiber nonlinearity induced by large launch power can be mitigated. We experimentally demonstrate a transmission of 120 Gbps 16-QAM SSB signal in C-band over an 80-km single mode fiber (SMF) without optical inline amplifier and pre-amplifier.

The branch-line coupler (BC) circuit of miniaturized configuration using periodically installed open circuit stabs was designed onto an electro-optic (EO) crystal, LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , substrate at 10 GHz. The operation as the 90 degree hybrid was confirmed at around the center frequency by the experiment. By using this BC circuit as the signal power divider, we proposed a compact EO single sideband (SSB) modulator. The SSB modulator was designated and fabricated for 1550 nm light wavelength. In the experiment, the optical SSB signal with the sideband suppression ratio of about 30 dB was observed.

Carrier generation and IF signal up-conversion using optical injection locking and stimulated Brillouin scattering

Optical single sideband modulation with tunable optical carrier-to-sideband ratio using DP-BPSK modulator

Single side-band (SSB) technologies are especially useful in optical fiber communication systems, such as higher density wavelength multiplexing and long-haul fiber transmission due to less nonlinear optical effects, because of the reduced optical power. This letter reports on the SSB modulation performance of a LiNbO/sub 3/ integrated modulator consisting of four phase modulator waveguides. Optical SSB modulation with suppressions of main carrier (-22.6 dB) and J/sub 3/ subcarrier (-18.4 dB) of a 10-GHz single-tone signal with a driving voltage of 6.3 V/sub p-p/ was demonstrated. The total insertion loss was 10.6 dB.

Optical single sideband (OSSB) signals are conventionally generated using a dual-drive Mach–Zehnder modulator (MZM) or by using a single-drive MZM in conjunction with a fibre Bragg grating filter. In this study, the authors propose and mathematically characterise a novel radio over fibre downlink in which an OSSB signal is generated using a single-drive, rather than dual-drive, MZM without any additional filter. Additionally, their proposed scheme can achieve optical upconversion of the electronic signal. Furthermore, in addition to cost advantages, the proposed scheme's bit error ratio (BER) performance is better than the classical OSSB signal generation scheme.

It is proposed a novel spectroscopy to make a resolution higher with an optical single-sideband (SSB) modulator. It has been experimentally cleared that the system resolution becomes higher order at ~MHz.

Autonomous driving technology relies on in-vehicle radar, which plays a crucial role in detecting surrounding objects.However, in environments with multiple radars, radio interference can degrade radar performance.This paper proposes a real-time frequency measurement method based on single sideband (SSB) modulation, requiring only two instantaneous sideband values for accurate measurement.The feasibility and accuracy of the proposed method were experimentally demonstrated.