SSB Modulation Research Articles

Real-time 60 Gb/s PS-64QAM SSB-DMT transceiver deploying a low-complexity distribution matcher in band-limited IM-DD system

In this work, we have implemented a low-complexity distribution matcher in real-time for bandwidth-limited intensity modulation and direct detection (IM/DD) system based on field programmable gate array (FPGA). For the hardware implementation of probabilistic shaping (PS), a simple and effective distribution matcher is the key to achieving the symbol of the target probability. Compared to traditional PS distribution matchers, our proposed distribution matcher has lower hardware implementation complexity and only requires a small amount of look-up table and registers to achieve target probability distribution. Meanwhile, an optical tunable filter is used to generate single sideband discrete multitone (SSB-DMT) signals for 50-km standard single-mode fiber (SSMF) transmission. By using PS technology and SSB modulation scheme, we successfully real-time realize 11-GHz PS-64QAM SSB-DMT signals over 25/50-km SSMF transmission in band-limited IM-DD system, achieving a line rate of approximately 65.7 Gbit/s.

In-band full-duplex multiband mobile fronthaul network based on analog radio-over-fiber andtandem SSB modulation.

An in-band full-duplex multiband mobile fronthaul network is proposed based on analog radio-over-fiber and tandem single-sideband (TSSB) modulation. Two optical carriers with a wavelength spacing of 50GHz in accordance with international telecommunication union dense wavelength division multiplexing (DWDM) standards are employed in each distributed unit (DU): one is used to carry two different radio frequency (RF) vector signals at 3 and 10GHz, while the other is used to carry a vector signal at 15GHz and a single-tone signal at 15GHz. At the DU, a parallel TSSB modulation is applied, which eliminates the cross talk of TSSB modulation through two dual-polarization binary phase-shift keying (DP-BPSK) modulators. This allows the two vector signals carrying different data to be distributed on both sides of the optical carrier. At the active antenna unit (AAU), different RF vector signals centered at 3, 30, and 60GHz, each carrying distinct information, can be generated by selecting either one DWDM channel or two adjacent DWDM channels in a group. By utilizing the spacing between the two DWDM optical carriers, millimeter-wave signals can be generated without the need for additional electronic upconversion devices in the AAU. In the uplink, a DP-BPSK modulator is used to receive the signal of interest while canceling self-interference. Simulation results demonstrate the performance of the proposed system. After transmitting 25km through single-mode fiber and compensating for dispersion using corresponding dispersion-compensating fiber, the downlink and uplink achieve error vector magnitudes of less than 9% and 2%, respectively, when the receiving optical power is 6dBm.

Single-sideband Suppressed-carrier Modulation and Demodulation: Principles, Analysis, Circuits, and Applications

This comprehensive article provides an in-depth exploration of single-sideband (SSB) modulation and demodulation techniques. The article discusses the principles, fundamental methods, and circuits involved in SSB modulation, highlighting its efficiency as an analog amplitude modulation method for long-distance information transmission while effectively utilizing available bandwidth. A comparative analysis of various modulation methods, including conventional amplitude modulation, double-sideband (DSB)modulation, vestigial sideband (VSB) modulation, frequency modulation (FM), phase modulation (PM), and single-sideband (SSB) modulation, is presented. Furthermore, the article delves into the diverse applications of SSB analog amplitude modulation.

Scheme to eliminate the time shift of code edges based on the optimal transmission point of a DP-MZM.

To eliminate the time shift of code edges on a single-sideband (SSB) modulation signal transmission in a radio-over-fiber (RoF) system, a new, to the best of our knowledge, SSB modulation scheme based on an optimal transmission point for a double-parallel Mach-Zehnder modulator (DP-MZM) is proposed. The scheme is based on DP-MZM to realize the separation of the carrier and the +1st-order sideband at the optimal transmission point, and the baseband signal modulates the 2.5Gb/s data signal to the +1st-order sideband of the SSB signal; then, the carrier and the +1st-order sideband are transmitted with a carrier-to-sideband ratio of 0dB. Theoretical analysis shows that compared to the traditional SSB-modulated optical millimeter-wave signal generation scheme this scheme completely solves the problem of the time shift of code edges caused by dispersion. The simulation results show that the improved SSB modulation scheme has a Q factor of 23.362, the minimum bit error rate is 4.207×10-127 at 73.453km, and the eye diagram is still very clear. Under the premise of meeting the basic requirements of communications, the maximum communications distance can reach 135km, which is 270% of the transmission distance of a traditional SSB modulation model.Thus, the system performance has been greatly improved.

Broadband and linearized photonic time-stretch analog-to-digital converter based on a compact dual-polarization modulator.

A broadband linearization scheme for a photonic time-stretch (PTS) analog-to-digital converter (ADC) is proposed based on a dual-polarization binary phase-shift keying (DP-BPSK) modulator with complementary parallel single-sideband (SSB) modulation. In this system, two stretched radio frequency signals, corresponding to the two orthogonal polarizations of the DP-BPSK modulator, are complementary, which can realize differential operation to eliminate the second-order harmonic distortion and pulse envelope distortion. Meanwhile, SSB modulation is used to avoid dispersion-induced power fading. Theoretical analysis and simulation results show that the proposed scheme can effectively improve the linear performance of PTS ADC, even considering the polarization-dependent delay deviation and amplitude offset.

Wide Wavelength Selectable and High Frequency Precision of All-Optical Wavelength Conversion Using Pump Light Generated from Optical Combs and SSB Modulation

All-optical wavelength conversion based on four-wave mixing (FWM) in highly nonlinear fiber (HNLF) with wide wavelength selectivity and highly precise frequency controllability was investigated in combination with pump light generated from optical combs and single-side-band (SSB) modulation. Using multiple carriers, optical combs generated using LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> phase modulators and an SSB phase modulator, pump lights were precisely controlled with a frequency range of 580 GHz and frequency shift of 1.25 GHz. The frequency difference of the pump lights from the ideal one was less than the resolution of an optical spectrum analyzer FWM was performed for single-polarized 10 Gbaud NRZ-QPSK signals in combination with the generated pump lights, and clear eye-openings and constellations for idler signals were achieved. Moreover, a bit error rate (BER) of <3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> for all idler lights was achieved. Conversely, in the case of the 1.25 GHz controlled pump light, the constellation was distorted, and the BER was saturated at 2.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> . In addition, the limit of wavelength convertible bandwidth was investigated to determine the condition for selecting the frequency of wavelength conversion applicable to wavelength defragmentation in the metro/core networks. From the experimental and analytical results, the maximum frequency spacing between the signal and pump was found to be 1403.125 GHz, limited by the wavelength conversion efficiency of the HNLF, whereas the minimum frequency spacing was found to be 25 GHz, restricted by the crosstalk between the signal and pump light that could not be eliminated using the bandpass filter.

Asymmetric dual-SSB modulation for photonic co-frequency mm-wave signals generation and DSP-free receiver.

An asymmetric dual-single-sideband (SSB) modulation scheme for photonic co-frequency millimeter (mm)-wave signals generation and digital signal processing (DSP)-free receiver is experimentally demonstrated for the first time, to the best of our knowledge. To effectively avoid the sideband crosstalk in the traditional symmetric dual-SSB modulation scheme, not only two vector-modulated signals but also two unmodulated sidebands are modulated on the two asymmetric sides of an optical carrier in this scheme. An optical delay line interferometer could easily separate these two asymmetric dual-SSB signals simultaneously in the receiver, and thus the photonic frequency up-conversion is realized. Besides, this scheme is free of dispersion-induced RF power fading thanks to the SSB modulation. By this means, no digital compensation algorithms such as carrier phase recovery, fiber dispersion compensation, and channel equalization are required, contributing to the DSP-free receiver. In our experiment, two 32 GHz 3.2 Gb/s 16-ary quadrature amplitude modulation mm-wave signals are produced using two RF signals with the carrier frequencies of 12 GHz and 20 GHz. The error vector magnitude (EVM) performances of these two mm-wave signals after 25.5 km standard single-mode fiber transmission are better than 3rd Generation Partnership Project requirements without using any digital compensation algorithms.

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.

Performance vs. Spectral Properties for Single-Sideband Continuous Phase Modulation

This study revokes the performance of continuous phase modulation (CPM) able to generate a single-sideband (SSB) spectrum directly. This signal is analyzed in terms of modulation indices, pulse lengths, and pulse widths, all of which affect error probability, bandwidth, SSB property, and receiver complexity. The error probability performance is based on an approximation of the minimum Euclidean distance. A numerical power spectral density calculation for this particular SSB modulation in terms of the modulation index is presented. Reasonable tradeoffs in designing modulation schemes have been proposed using multi-objective optimization to ensure sizable improvements in bit error rate (BER), spectral efficiencies, and complexity without losing the property of being a SSB signal. Performance comparisons are made with known CPM schemes, e.g., Gaussian Minimum Shift Keying (GMSK) and Raised Cosine based CPM (RC).

Filter-Free Photonic Image-Rejection Down-Conversion for Distributed Antenna Applications

Photonics-assisted frequency conversion based on cascaded modulators is an effective way to satisfy the requirements of distributed antenna array applications. A filter-free photonic image-rejection down-converter with immunity to dispersion-induced power fading is proposed and demonstrated. The radio frequency (RF) signal from the distributed antenna unit is injected into a dual-drive Mach–Zehnder modulator (DDMZM) through an electrical 90° hybrid coupler (HC), and a single-sideband (SSB) signal is realized. It is then transmitted to the center office by an optical fiber link. At the center office, the modulated RF signal is injected into a dual-polarization dual-parallel MZM (DP-DPMZM) after a polarization controller (PC). Afterwards, an LO signal remodulates it through the Y-DPMZM, and carrier-suppressed SSB modulation is fulfilled via another electrical 90° HC. After the power splitting, quadrature I and Q IF signals can be obtained by a photonics-based continuously adjustable phase shifter. Through a combination of the I/Q IF signals with a low-frequency electrical 90° HC, a photonics image-rejection down-converter based on phase cancellation is realized. Moreover, no optical filter is required; thus, the image-rejection down-converter can work with a large bandwidth. The proposed filter-free photonic image-rejection down-converter is theoretically analyzed and experimentally verified.

Peak-to-Average Power Ratio Reduction of Carrier-Suppressed Optical SSB Modulation: Performance Comparison of Three Methods

We compare the performances of three previously proposed methods to reduce the peak-to-average power ratio (PAPR) of the carrier-suppressed optical single-sideband (OSSB-SC) signal. PAPR of OSSB-SC signal becomes high due to the peaky Hilbert-transformed signal which is used for spectral suppression. Nonlinear phase shifts induced by high PAPR degrade OSSB-SC signal during fiber transmission. Previously, we proposed peak folding, peak clipping, and high-pass Hilbert transform methods to reduce the PAPR of OSSB-SC modulation. In this study, we numerically compare the effectiveness of proposed methods in a 10 Gbit/s non-return-to-zero (NRZ)-coded 100-km single-channel transmission link. Due to the reduced PAPR, peak folding and peak clipping can increase the self-phase modulation (SPM) threshold of the studied system by 2.40 dB and 2.63 dB respectively. The high-pass Hilbert transform method improves the SPM threshold by more than 9 dB.

Single Sideband Hartley Amplitude Modulation

It is developed a method of information transmission with application of amplitude Single Sideband Hartley modulation (SSBH) allowing to increase of radio channel length for optical and fiber optic signal transmission systems where single sideband amplitude modulation (SSB) is used. Increase of communication range is provided due to application a sum of two orthogonal oscillations of the same frequency as a carrier (Hartley wave). It provides energy gain in 6 dB and 1.41 times increase of the amplitude of output signal of synchronous detector comparing to SSB in case of the same radiation power of transmitter and the same sensitivities of SSBH and SSB signals receivers. Application of SSBH and SSB modulation allows to provide the energy gain in transmitting channel approximately 15–20 times comparing to amplitude modulation (AM) application. It also provides increased security of SSBH transmission since in case of absence of modulation signal the transmitter does not radiate, that allows to provide energy saving in case of transmitter power supply with battery. Depending on the need we can use both upper and lower side bands.

Integrated Optical SSB Modulation / Frequency Shifting Using Cascaded Silicon MZM

A frequency conversion mixer or single side band modulator using two cascaded MZM is proven experimentally. The operation of the circuit is modelled by a transfer matrix approach and verified by simulation in support of the experiment. A 10 GHz shift of the optical carrier in both left and right direction is demonstrated. The residual sideband suppression relative to the enhanced sideband is 22 dB for the best cases. Numerical analysis shows that the circuit has 3-dB optical and 3-dB electrical intrinsic advantage over the functionally equivalent DP-MZM.

Optical Single-Sideband Modulation with Tunable Optical Carrier-to-Sideband Ratio Based on a Dual-Polarization Mach–Zehnder Modulator and a Polarizer

We propose and experimentally demonstrate a novel and simple approach to implementing optical single-sideband (OSSB) modulation with tunable optical carrier-to-sideband ratio (OCSR) based on a dual-polarization Mach–Zehnder modulator (DPol-MZM) and a polarizer (Pol). In this scheme, the light wave is modulated by radio frequency (RF) signal with SSB modulation in the upper arm of the DPol MZM, while the light wave in the lower arm is not modulated. Therefore, a partial polarization orthogonal SSB (PPO SSB) modulated signal is generated at the output of the DPol MZM without using an optical band-pass filter (OBPF). The PPO SSB signal is then sent to a Pol through a polarization controller. By simply adjusting the polarization state, the OSSB modulation with tunable OCSR can be realized. The experimental results show that an OSSB-modulated signal with adjustable OCSR from – 35 to 55 dB can be achieved. Besides, the proposed scheme features the merit of wideband tunability, where the radio frequency (RF) can be operated from 3 to 17 GHz.

D-band signal generation without optical filter based on Carrier Suppressed Frequency Eightfold

We proposed a new scheme to realize D-band signal generation without optical filter based on Carrier Suppressed Frequency Eightfold (CSFE) in a radio over fiber (RoF) system. The carrier suppressed frequency eightfold is used to generate two optical tones with channel spacing of 8xRF frequency at D-band, and the SSB modulation is realized by using one intensity modulator. In our scheme, no any optical filter is needed, which greatly reduces the system complexity. With the proposed scheme, we successfully demonstrated the 150 GHz 10GBaud QPSK signal and 4GBaud 16QAM signal delivery over 10-km SMF and 1 m wireless.

A Scalable Four-Channel Frequency-Division Multiplexing MIMO Radar Utilizing Single-Sideband Delta–Sigma Modulation

A scalable four-channel multiple-input multiple-output (MIMO) radar that features a modular system architecture and a novel frequency-division multiplexing approach is presented in this article. It includes a single 30-GHz voltage-controlled oscillator (VCO) for the local oscillator signal generation, four cascaded 120-GHz transceivers with a frequency quadrupler, and on-board differential series-fed patch antennas. The utilized uniform antenna configuration results in 16 virtual array elements and enables an angular resolution of 6.2°. The vector modulators in the transmit (TX) paths allow the application of complex bit streams of second-order delta-sigma modulators easily generated on a field-programmable gate array (FPGA) to implement single-sideband (SSB) modulation on the TX signals resulting in orthogonal waveforms for the MIMO operation. Only one phase-locked loop and no digital-to-analog converter is required. The waveform diversity also allows the simultaneous transmission of the TX signals to reduce the measurement time. The application of the SSB modulation on the frequency-modulated continuous-wave MIMO radar requires only half of the intermediate frequency bandwidth compared with the double-sideband modulation. The issue of the phase and amplitude mismatches at the virtual array elements due to the scalable radar architecture is addressed and a calibration solution is introduced in this article. Radar measurements using different numbers of virtual array elements were compared and the digital-beamforming method was applied to the results to create 2-D images.

RF pilot tone phase noise cancellation based on DD-MZM SSB modulation for optical heterodyne RoF link

The optical heterodyne radio over fiber (RoF) link using single-sideband (SSB) modulation has advantage in system scalability, tunability, as well as resistance to chromatic dispersion induced frequency selective fading. However, the phase noise which seriously degrades system performance, is a major obstacle to employ low-cost free-running lasers in the aforementioned link. In this paper, the RF pilot tone (RFP) phase noise cancellation (PNC) based on dual drive Mach–Zehnder modulator SSB modulation for optical heterodyne RoF link is investigated and demonstrated. Two kinds of RFP PNC schemes, carrier whole multiplication (CWM) and carrier signal multiplication (CSM), are both derived theoretically and verified experimentally. The impacts of carrier signal power ratio, carrier filter bandwidth and guard band on system performance are studied in detail. The results show that, the RFP-CSM scheme can improve the spectral efficiency by 62.5% and receiver sensitivity of 1.2 dB for 1.25 Gbps quadrature phase shift keying signal at a BER of 3.8 ×10−3, as compared with the RFP-CWM scheme and power detection scheme, mainly attributed to the absence of the second-order nonlinear intermodulation distortion. Furthermore, the RFP-CSM scheme demonstrates good phase noise robustness with different high-order modulation formats under two kinds of linewidth local oscillator lasers.

Dual-frequency light source with widely tunable frequency difference based on single-side-band modulator

A dual-frequency light source at 1550 nm with widely tunable frequency difference is proposed and experimentally demonstrated. Two beams are split from the same single-frequency source and then modulated by two parallel single-side-band (SSB) modulators respectively for +1-order or -1-order sideband. The dual-frequency light source is obtained by recombining the two sidebands. In this scheme, the wide bandwidth of SSB modulator guarantee the widely tunable frequency difference. Simultaneously, the parallel SSB modulators construction makes it true that the dual-frequency light source with low minimum beat frequency can be easily obtained. A dual-frequency light source with 40 kHz to 30 GHz tunable frequency difference is experimentally demonstrated in this work. The signal-to-noise ratio (SNR) of beat signals is over 30 dB. Meanwhile the standard deviation of frequency differences in 100 min is 0.9234, 2.42194 and 5.59017 for dual-frequency all-fiber laser with 100 MHz, 25 GHz and 50 kHz frequency difference respectively.

A Fast Linearly Wavelength Step-Swept Light Source Based on Recirculating Frequency Shifter and Its Application to FBG Sensor Interrogation.

A wavelength step-swept light source (WSSL) using a recirculating frequency shifter loop (RFSL) based on a single-side-band (SSB) modulator is proposed, in order to achieve a linear and fast wavelength-sweeping. The swept step can be tuned from 1.2 pm to 128 pm by adjusting a precise and stable radio frequency (RF) signal that is applied to the SSB modulator. The swept rate can be tuned up to 99 kHz in a range of over 5.12 nm. Wavelength-to-time mapping is used to measure static strain-induced or temperature-induced shifting of the reflected central wavelength of a fiber Bragg grating (FBG). Because of the high linearity of the light source, the interrogation linearity of the strain and the temperature are as high as 0.99944 and 0.99946, respectively. When a dynamic periodic strain applied to FBG sensor, the dynamic performance of the FBG sensor is successfully recorded in the time domain and its power spectral density of a fast Fourier transform (FFT) is calculated. The signal-to-noise ratio (SNR) of the power spectral density is over 40 dB for a 100 Hz dynamic strain and the calculated sensitivity is 0.048 με/Hz1/2. A sharp change in the strain frequency from 100 Hz to 500 Hz is captured in real time.

Harmonic PMU Algorithm Based on Complex Filters and Instantaneous Single-Sideband Modulation

Phasor measurement units (PMUs) have become powerful monitoring tools for many applications in smart grids. In order to address the different issues related to harmonics in power systems, the fundamental phasor estimator in a PMU has been extended to the harmonic phasor estimator by several researchers around the world. Yet, the development of harmonic phasor estimators is a challenge because they have to consider time-varying frequencies since the frequency deviation in the harmonic components is proportional to the harmonic order in a dynamic way. In this work, a new algorithm for harmonic phasor estimation using an instantaneous single-sideband (SSB) modulation is presented. Unlike other SSB-based approaches, its implementation in this work is based on concepts of instantaneous phase and instantaneous frequency. In general, the proposed algorithm is divided into two stages. Firstly, the estimation of the fundamental phasor is carried out by means of a complex finite impulse response (FIR) filter which provides the analytic signal used to compute the instantaneous magnitude, phase, and frequency. Secondly, a complex FIR filter bank is proposed for the estimation of the harmonic components, where the instantaneous SSB modulation technique is applied in order to center the harmonic components into specific narrow bands for each complex filter when an off-nominal frequency occurs. The validation of the proposed algorithm is carried out by means of the current standards of phasor measurement units, i.e., Std. C37.118.1-2011 and C37.118.1a-2014, which involve steady-state, dynamic, and time performance tests.