Single-sideband Modulation Research Articles

A linearized optical single-sideband modulation RoF link with tunable optical carrier-to-sideband ratio

In this paper, an optical single-sideband (OSSB) modulation radio over fiber (RoF) link with tunable optical carrier-to-side-band ratio (OCSR) and simultaneous third-order intermodulation distortion (IMD3) and power fading suppression is proposed. In the proposed link, a phase-modulated signal and an optical carrier are polarization multiplexed using a Sagnac loop. The periodic power fading caused by chromatic dispersion is avoided by filtering the lower sideband. By adjusting the polarization state, the IMD3 is suppressed and a tunable OCSR can be achieved. Compared with the traditional Mach–Zehnder modulator (MZM) based link, the spurious free dynamic range (SFDR) of the proposed link is improved by more than 18 dB with different RF frequencies. In the broadband characteristic test, the proposed link exhibits lower error vector amplitude (EVM) and higher adjacent channel power ratio (ACPR) in a larger input RF power range.

Broadband and High-Capacity Silicon Photonics Single-Sideband Modulator

We propose a novel photonic-integrated single-sideband (SSB) modulator realized in silicon on insulator technology operating either in suppressed-carrier or full-carrier mode with continuously tunable carrier-to-sideband ratio (CSBR). Large rejection levels of the spurious sidebands and residual carrier in excess of 40&#x00A0;and 30&#x00A0;dB, respectively, with a CSBR tunability over a <inline-formula><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>&#x00A0;50&#x00A0;dB range, are demonstrated. By employing a single silicon photonics (SiP) phase modulator and a compact and high-performance filtering element, the proposed architecture exhibits a compact layout and tolerates high driving voltage levels, leading to large OSNR values of the modulated sideband in excess of 50&#x00A0;dB. The device supports broadband RF data signals and its operation is tested with an up to 5&#x00A0;Gbps ASK-modulated carrier at 16.5&#x00A0;GHz, limited by available RF equipment. Furthermore, the technique allows to implement a frequency-multiplication mechanism for the input RF carrier, and up to threefold effective bandwidth enhancement of the SiP modulator is obtained by generating an optical SSB signal with a modulated spectral component spaced by 49.5&#x00A0;GHz from the optical carrier. Such features are promising for implementing cost-effective optical distribution of millimeter-wave wireless data signals supporting the evolution of next-generation radio access networks.

Analysis of Optical Single Sideband Modulators for Radio Over Fiber Link with and without Second Order Sidebands

The analysis of Optical Single Sideband (OSSB) generation with and without second-order sidebands for Radio over Fiber (RoF) is presented. The performance of systems based on hybrid coupler with distinct phase angle and Dual-Parallel Dual-Drive Mach-Zehnder Modulator (DP-DDMZM) is compared using simulation. Impact of parameters like Single-Mode Fiber (SMF) length, Radiofrequency (RF) amplitude, and laser linewidth on Signal-to-Noise Ratio (SNR) has been investigated. It has been observed that eliminating one of the second-order sidebands with 120° hybrid coupler improves peak SNR in comparison to 90° hybrid coupler with both second-order sidebands and DP-DDMZM-based system without second-order sidebands irrespective of Continuous Wave (CW) laser linewidth.

D-band signal generation and transmission without optical filter based on optical carrier suppression and single-sideband modulation.

We experimentally demonstrated a novel and simple scheme to generate D-band millimeter-wave (mm-wave) signal without optical filter based on optical carrier suppression (OCS) and single-sideband (SSB). One intensity modulator (IM) driven by radio frequency (RF) signal at 50 GHz is firstly employed to generate two tones with channel spacing of 2 x RF frequency based on OCS. Another subsequent in-phase/quadrature (I/Q) modulator driven by RF signal at 30 GHz is then applied to generate SSB signal by using independent sideband (ISB). No optical filter is needed so that the whole system can be simplified. After using a D-band photomixer for detection, we finally generated the vector mm-wave at 130 GHz. Based on the proposed system, 4-Gbaud/8-Gbaud quadrature phase shift keying (QPSK) information carried by the generated D-band mm-wave signals were transmitted over 22.5-km single model fiber (SMF) and 1-m wireless distance radio-over-fiber (ROF) link. Bit-error-ratio (BER) performances under hard/soft-decision forward-error-correction (FEC) threshold are shown respectively in cases of two different signals transmission rates.

Transmission of dual-chirp microwave signal over fiber with suppression chromatic-dispersion-induced power-fading based on stimulated Brillouin scattering

We report a microwave photonic link to transmit dual-chirp microwave signals over fiber based on stimulated Brillouin scattering (SBS) using a dual-polarization Mach–Zehnder modulator (DPol-MZM). The DPol-MZM is driven by a radio frequency (RF) carrier and a baseband single-chirp waveform to realize carrier-suppressed single-sideband (CS-SSB) modulation based on SBS. The dual-chirp waveforms centered at 12.4 GHz and 15.5 GHz with bandwidths of 0.4 GHz have been successfully generated. In our link, the CS-SSB modulation based on SBS is performed to overcome fiber chromatic-dispersion-induced power fading (CDIP). The proposed scheme is theoretically analyzed and experimentally verified.

High Modulation Efficiency and Dynamic Range Optical Single Sideband Modulation Without Gain Penalty in Nonlinear Distortion Suppression

The optical single sideband (OSSB) modulation with tunable optical carrier to sideband ratio (OCSR) is a promising and popular technique in wideband analog signal transmission and microwave signal processing, which can improve modulation efficiency and combat the fiber chromatic dispersion. However, in all reported schemes for achieving OSSB modulation with tunable OCSR, the spurious free dynamic ranges (SFDR) of the systems are all limited by the third-order intermodulation distortion (IMD3). In this paper, our object is to improve the SFDR and suppress the IMD3 in a novel OSSB modulation with tunable OCSR. The proposed system consists of a primary channel and a secondary channel. In primary channel, an OSSB modulation with tunable OCSR is implemented. In secondary channel, the optical carrier and first-order sidebands are perfectly cancelled out, which can suppress the IMD3 without gain penalty at the same received optical power. In this way, a large-SFDR OSSB modulation with tunable OCSR is realized. Experimental results exhibit that the IMD3 gets effective cancellations without gain penalty under unchanged total received power, and the output microwave signal power obtains about 11-dB improvement by optimizing the OCSR. A greatly increased SFDR of over 128 dBHz4/5 is achieved in the proposed system.

Development of a Doppler-broadened NICE-OHMS system for trace gas detection based on a single sideband phase modulator

To expand the applicability of noise-immune cavity-enhanced optical heterodyne molecular spectrometer (NICE-OHMS), a universal system incorporating a fiber-coupled single-sideband modulator (f-SSM) for control of the laser frequency has been developed. A homemade PID servo mainly composed of two integrators has been designed, resulting in a locking bandwidth of 170 kHz and a continuous tuning range of 2.2 GHz. The system exhibits a noise-equivalent Doppler-broadened absorption limit of 8.0×10−14 cm−1 for an integration time of 64 s. Since the f-SSM is the sole external frequency actuator, this opens up for NICE-OHMS based on a multitude of laser systems.

Coherent UD-WDM RoF Fronthaul Network With D-EML Transmitter and Phase-Noise Robust Receiver

This work proposes and tests a simplified coherent uplink architecture for ultra-dense coherent analog mobile Fronthaul with phase noise cancellation based on single sideband modulation of a dual-EML. Results show optical channel spacings of only 1.5 GHz and error-free signal recovery with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \nu $ </tex-math></inline-formula> Tb = 1.2% and 3% with reaching power as low as −46dBm for 100 Mbit/s and −38 dBm for 1 Gbit/s using QPSK modulation.

Photonic-based analog and digital RF self-interference cancellation with high spectral efficiency.

A photonic-assisted analog and digital radio frequency (RF) self-interference cancellation (SIC) approach with high spectral efficiency is reported for base stations in in-band full-duplex radio-over-fiber systems on the basis of our previous research. One dual-polarization quadrature phase-shift keying (DP-QPSK) modulator is used as the canceller for one base station. The two dual-parallel Mach-Zehnder modulators of the DP-QPSK modulator are both biased as carrier-suppressed single-sideband modulators and driven by the received signal and reference signal, respectively, to achieve high spectral efficiency while implementing the SIC in the optical domain. The baseband optical signal after SIC is further transmitted to the central station, where the electrical signal is recovered, sampled, and processed to further suppress the residual self-interference in the digital domain by using the recursive least-square (RLS) algorithm. An experiment is then performed. The proposed system is demonstrated by employing two independent channels. The analog cancellation depths of the 200, 500, and 800 Mbaud QPSK-modulated self-interferences are around 24, 20, and 20 dB, respectively; the total cancellation depths are around 29, 28, and 25 dB, respectively, when the analog cancellation and the RLS algorithm digital cancellation are applied. Meanwhile, the fiber distribution has no significant influence on SIC performance.

Spectrum Aggregation Dual-Band Real-Time RF/Microwave Analog Signal Processing From Microstrip Line High-Frequency Hilbert Transformer

A uniplanar microstrip line RF/microwave real-time analog signal processing (RAP) units are proposed in this article to operate concurrently at two frequencies for spectrum aggregation applications. First, a fundamental building block novel microstrip line dual-band Hilbert transformer (DBHT) is developed by integrating a dual-band 180° coupler and a dual-band delay line (DBD). The theoretical analysis is carried out to determine the relation of coupler and delay line forming closed loop resonance in the proposed circuit topology. Then, a dual-band edge detector from DBHT and a dual-band single-sideband (DBSSB) modulator composed of dual-band power divider/combiner (DBPD/DBPC), DBHT, and DBD are developed for dual-band real-time RF/microwave signal processing. To verify the proposed concept, a prototype of microstrip line DBHT working at 0.9 and 1.98 GHz is designed, and the measurement and simulation agree well with theoretical analysis. To demonstrate the real-time RF/microwave analog signal processing, a dual-band edge detector composed of DBHT is verified in the experiment. Furthermore, a prototype of microstrip line DBSSB modulator is fabricated and validated in the experiment to demonstrate the real-time single-sideband modulation at two concurrent RF/microwave frequencies.

Transmission of 3D Holographic Information via Conventional Communication Channels and the Possibility of Multiplexing in the Implementation of 3D Hyperspectral Images

This paper shows the possibility of transmitting 3D holographic information in real time with a TV frame rate over conventional radio channels by transmitting two two-dimensional signals in two image modes: depth map and surface texture of the object (mask + texture). The authors point out that it is similar to compression through eliminating the carrier and it is inherently similar to SSB (single-sideband modulation) but has higher resolution ability in reconstructing 3D images. It is also shown that such technology for transmitting 3D holographic information is in good agreement with the tasks of both aggregating and multiplexing 3D images when they are transferred from one part of the electromagnetic spectrum of radiation to another and the creation of hyperspectral 3D images.

Performance Analysis Of Optical Modulation Techniques Based On Reduction Of Second Order Harmonics And Chromatic Dispersion on OFDM Signals

ABSTRACT This work explains the theoretical and mathematical investigations of the transmission performance of an optical Single Sideband (SSB) modulation technique generated by a Mach Zehnder Modulator (MZM) with a 90° and 120° phase shift using hybrid coupler (Modified SSB) in addition to the Vestigial Sideband technique (VSB). The problem addressed in this paper is the effect of non-linearity of the transmitter system and the chromatic dispersion in single mode fiber due to the presence of second- and higher order harmonics. The non-linearity of the transmitter generates second and higher order harmonics, which affects the system performance leading to reduction in the data rate and increased distortion. The transmission performance of SSB, M-SSB and VSB is evaluated based on the extinction ratio of the MZM, different transmission lengths of the fiber, optical signal modulation index and the receiver sensitivity. A mathematical model has been developed for all the systems representing the modulation techniques till the second order. The baseband modulation consists of an RF signal of frequency 18 GHz and an Orthogonal Frequency Division Multiplexing (OFDM) signal with 4-QAM modulation technique converted to optical signal, using the MZM and transmitted over a SMF of distance of 75 Km. Our results show that the M-SSB technique proves to be more immune toward transmitter nonlinearity and chromatic dispersion as compared to its counterparts. In addition to this, it improves the receiver sensitivity by 6.56 dBm. The results generated by software simulation are in tandem with the mathematical model.

Performance optimization of RSOA based mm-wave radio-over-fibre access network

In this paper, a Reflective Semiconductor Optical Amplifier based, Radio-over-Fibre access network configuration has been proposed to feed future millimeter-wave radio systems. The system architecture combines several approaches to overcome the challenges of millimeter-wave signal transmission. Reflective semiconductor optical amplifier modulator realizes a colorless and relatively cost-effective Remote Antenna Unit. The same optical carrier is used for both downlink and uplink. Optical single-sideband modulation is used at the downlink, which is robust against chromatic dispersion, but the complex realization of this modulation format is not possible at the Remote Antenna Unit. Optical intermediate frequency transmission is applied at the uplink direction, and the required local oscillator signal originates from the central station. The critical element is the reflective optical amplifier, as it compensates for the optical loss and works as an external intensity modulator. The operation of the reflective optical amplifier is modeled by multisection rate and wave equation-based description. The amplification and modulation behaviors of an available reflective optical amplifier are also measured. The experimental work validated the colorless operation and the quality of the modulation versus bias current and input optical power. Finally, system simulation was realized. The uplink and downlink power budgets were balanced, and optimal values for the optical coupling rate and RSOA bias current have been selected.

A novel bidirectional RoF link with compensated SBS and RB for 16-QAM OFDM based mm-wave downlink and uplink vector signal generation and transmission on a single fiber

A novel bidirectional RoF link with compensated SBS and RB for 60 GHz OFDM-based 16-QAM downlink and uplink vector signal generation and co-propagation over a single fiber is proposed. At the central station (CS), 60 GHz optical mm-wave is generated and modulated in the optical single-sideband modulation (OSSB) technique by the 16-QAM OFDM downlink vector signal. At the base station (BS), the 60 GHz downlink signal is detected by a high-speed photodetector (PD). The 60 GHz electrical mm-wave signal is transmitted to the user end by an antenna. The uplink carrier is extracted from the unmodulated sideband of the mm-wave downlink vector signal. This reduces the complexity of BS and makes it free from the laser source. The 16-QAM OFDM-based mm-wave uplink signal is received from the user end through an antenna and down-converted to a 10 GHz uplink vector signal. The uplink signal modulates the extracted blank carrier in the OSSB technique. The uplink and downlink vector signals are co-propagated through the standard single bidirectional fiber. Although the carrier reuse over a single fiber reduces the fiber capacity by half, it generates non-linear backscattering such as Rayleigh Backscattering (RB) and Stimulated Brillouin Scattering (SBS). A theoretical analysis is made on the backscattered power and its effect on the fiber transmission. The compensation of SBS by maintaining the SBS threshold and mitigation of RB is carried out by appropriate modulation technique. In addition, downlink and uplink signal with different data rate is transmitted through the compensated bidirectional RoF link, and the transmission performance is analyzed. Based on the analysis, the theoretical model for simultaneous downlink and uplink signal transmission over a single fiber is proposed and verified by the software simulation. The compensated bidirectional RoF link shows up a better performance up to 75 km with negligible power penalty.

Dual-output filter-free microwave photonic single sideband up-converter with high mixing spur suppression.

A dual-output filter-free microwave photonic single sideband (SSB) up-converter with the mixing spurs highly suppressed is proposed and experimentally demonstrated. By introducing the balanced Hartley structure using a 90° optical hybrid, the lower sideband (LSB) and upper sideband (USB) up-converted RF signals can be generated simultaneously and output separately, with no need of either optical or electrical filtering. The structure avoids the special requirement with the optical modulation format of the local oscillator (LO) signal. The intermediate frequency signal is modulated with the optical carrier suppressed -SSB modulation format. The undesired optical components are highly suppressed. In this way, the high sideband and LO leakage suppression ratios of the SSB up-converter are guaranteed. The dual-output SSB up-conversion is experimentally achieved within the working frequency range of 10-30 GHz. The undesired sideband and LO leakage suppression ratios are larger than 67 dB for the whole frequency range. The spurious-free dynamic range of larger than 95.6dBc⋅Hz2/3 has also been achieved experimentally for both the LSB and USB up-conversion conditions.

Electromagnetically-Induced-Absorption-Mediated Ultrahigh-Rejection Microwave Photonic Notch Filter Using Single-Sideband Modulation

The inherent narrow bandwidth and wavelength-transparent nature of the stimulated Brillouin scattering (SBS) process make it a potential candidate for high-resolution wideband microwave photonic notch filters (MPNFs). The simplest way to realize a SBS-based MPNF is to use the narrowband Brillouin loss resonance with single-sideband modulation, where the modulation sideband is at the anti-Stokes frequency. However, using Brillouin loss with single-sideband modulation is highly inefficient because a large notch extinction requires large Brillouin loss, and thus, a large pump power. Here, we exploit an analogue of electromagnetically induced absorption (EIA) in the microwave domain to enhance MPNF rejection, at a fixed Brillouin pump power, by more than 6 orders of magnitude. We use this analogue of EIA to realize a MPNF with $&gt;75$-dB rejection up to 40 GHz, using a Brillouin loss of about 15 dB. We harness a coherent Brillouin interaction between the orthogonally polarized components of a probe, which is comprised of a laser carrier and a single-modulation sideband. Stimulated Brillouin scattering and other components used in our demonstration have recently been demonstrated on integrated platforms. The proposed scheme, therefore, has the potential for realizing efficient integrated microwave photonic notch filters with ultrahigh rejection.

DSP-free remote antenna unit in a coherent radio over fiber mobile fronthaul for 5G mm-wave mobile communication.

We propose a novel coherent analog radio over fiber (A-RoF) scheme to realize the generation, separation, and detection of four-independent mm-wave signals with the same carrier frequency on a single-wavelength for 5th generation (5G) mobile communication, and no digital signal processing (DSP) algorithms are required in remote antenna unit (RAU). In baseband unit (BBU), four-independent mm-wave signals are modulated on the two orthogonal polarization states of a single wavelength based on a dual-polarization IQ modulator using the dual single-sideband (SSB) modulation and polarization division multiplexing (PDM) technique. In RAU, a novel carrier polarization rotation module based on the self-polarization stabilization technique is proposed, and thus the four-independent mm-wave signals can be detected by self-coherent detection. Besides, the power fading effect induced by the chromatic dispersion could be overcome thanks to the optical SSB modulation, contributing to the increased coverage. By these means, no DSP algorithms are required in RAU, and the latency of signal processing could be significantly reduced. The experimental results show our proposed scheme could support 38.4 Gbps 16-ary quadrature amplitude modulation (16QAM) signals at 14 GHz over 30 km standard single-mode fiber (SSMF) transmission without DSP, satisfying 3rd Generation Partnership Project (3GPP) requirements. Besides, the measured error vector magnitude (EVM) value of 800 MBaud 16QAM signals at 28 GHz over 50 km SSMF transmission is 12.99%. This research provides a potential solution for the 5G mobile fronthaul.

Wideband Doppler frequency shift measurement and direction discrimination based on optical single sideband modulation with a fixed low-frequency reference signal

A wideband Doppler frequency shift (DFS) measurement and direction discrimination method based on optical single sideband (OSSB) modulation with a fixed low-frequency reference signal is proposed and experimentally demonstrated. In the proposed approach, the transmitted signal and the fixed low-frequency reference signal are applied to the lower and upper Mach–Zehnder modulators (MZMs) of a dual-drive dual-parallel MZM (DD-DPMZM) respectively, for realizing OSSB modulation independently. The echo signal is applied to a conventional MZM for optical double sideband (ODSB) modulation. A low-speed photodetector (PD) is used to implement optical-to-electrical conversion and generate three low-frequency beating signals. Both the value and direction of the DFS can be simply obtained by analyzing the frequencies of the three low-frequency beating signals. The proposed scheme has a simple structure, a wideband operating frequency range, and a low requirement of the receiving circuit. Experiments demonstrate that wideband DFS measurement and direction discrimination within 5∼18 GHz with a measurement error of less than ±0.06 Hz are achieved by using a 20 MHz reference signal.

Demonstration of enhanced four-wave mixing by harnessing stimulated Brillouin scattering within a suspended cascaded microring resonator

We experimentally demonstrate the enhanced four-wave mixing (FWM) by harnessing the forward stimulated Brillouin scattering (FSBS) within a silicon-based cascaded racetrack microring resonator (MRR). The frequency spacing of the split resonant peaks is precisely designed to match the Brillouin frequency shift (BFS). The cooperative interaction of the FSBS resonance and cascaded MRR resonance achieves an FWM enhancement of 2.97 and 2.43 dB for anti-Stokes and Stokes sidebands under the launched pump power of 35.48 mW and probe power of 17.78 mW. The BFS from 3.34 to 7.13 GHz is demonstrated by changing the waveguide width. Moreover, we show that this same system behaves as a single-sideband modulator, providing more than the 17 dB single-sideband rejection ratio under the condition that the probe light and Stokes are resonant in the cascaded MRR. Building on these results, this device opens the door to new types of all-silicon Brillouin laser, amplifier, isolator, and single-sideband modulator.

Simultaneous frequency and bandwidth doubling linearly chirped waveform generation based on cascaded phase modulator and dual-output dual-parallel Mach-Zehnder modulator

An approach to generate the linearly chirped microwave waveform with simultaneous frequency and bandwidth doubling by using cascaded phase modulator and dual-output dual-parallel Mach-Zehnder modulator (DO-DPMZM) is proposed. The lightwave emitted from a laser diode is firstly modulated by a splitting parabolic signal to realize a symmetric-triangle linear frequency sweeping light. The frequency sweeping light is then sent to a DO-DPMZM driving by a radio frequency (RF) signal. By properly setting the direct current biases of two sub-modulators, single sideband modulation is realized at each output of the DO-DPMZM. By introducing a time delay in one branch of the modulator’s outputs, a linearly chirped microwave waveform with both frequency and bandwidth doubling can be generated after optical-to-electrical conversion. The central frequency and bandwidth of the generated waveform can be easily adjusted by tuning the frequency of the RF signal and electrical coding signal of the arbitrary waveform generator. The linearly chirped microwave waveforms with bandwidth of 10 GHz and central frequency of 30 GHz or bandwidth of 12 GHz and central frequency of 40 GHz are numerically generated. Due to the simple structure and flexible tunability, the proposal may find applications in future high resolution radar systems.