KEYWORDS: Modulation, Radio over Fiber, Phase modulation, Heterodyning, Optical resolution, Signal generators, Modulators, Analog electronics, Signal detection, Optical amplifiers
We propose and experimentally demonstrate a potentially simple and cost-effective optical multi-carrier source based on electro-absorption modulated laser (EML) cascaded with phase modulator (PM) driven by synchronous sinusoidal radio-frequency (RF) signal, which can generate 10 subcarriers with frequency spacing of 12.5 GHz and power difference less than 3 dB. We further experimentally demonstrate a novel W-band radio-over-fiber (RoF) system based on EML cascaded with PM, which can realize the generation and transmission of 25-Gb/s quadrature-phase-shift-keying (QPSK) modulated millimeter-wave (mm-wave) signal at 100 GHz adopting optical remote heterodyning and heterodyne coherent detection. The bit-error ratio (BER) after 80-km single-mode fiber-28 (SMF-28) transmission and 2-m wireless delivery can be less than the forward-error-correction (FEC) threshold of 3.8×10-3.
We summarize the enabling technologies for broadband millimeter-wave communication at W-band. These enabling technologies include photonics-aided broadband signal generation, high-spectral efficiency modulation format, multiple-input multiple-output (MIMO) reception, high gain antenna, optical and electrical multi-carrier modulation, antenna polarization multiplexing and multi-band multiplexing, advanced digital signal processing (DSP), and heterodyne detection. Based on these advanced technologies, we have realized over 400G wireless signal transmission and over 2.5-km wireless delivery with a bit rate up to 50Gb/s at W-band.
We achieve several field trial demonstrations of ultra-wideband W-band millimeter-wave (mm-wave) signal generation and its long-distance air space transmission based on some enabling technologies and advanced devices. First, we demonstrated photonics generation and up to 1.7-km wireless delivery of 20-Gb/s polarization division multiplexing quadrature phase shift keying (PDM-QPSK) signal at W-band, adopting both optical and antenna polarization multiplexing. Then, we demonstrated photonics generation and up to 300-m wireless delivery of 80-Gb/s PDM-QPSK signal at W-band, adopting both optical and antenna polarization multiplexing as well as multi-band multiplexing. We also demonstrated photonics generation and up to 100-m wireless delivery of 100-Gb/s QPSK signal at W-band, adopting antenna polarization multiplexing.
We propose and experimentally demonstrate several different approaches for the realization of over 100Gb/s fiberwireless integration system, including optical PDM combined with MIMO reception, advanced multi-level modulation, optical multi-carrier modulation, electrical multi-carrier modulation, antenna polarization multiplexing and multi-band multiplexing. These approaches can effectively reduce the signal baud rate as well as the required bandwidth for optical and electrical devices. We also experimentally investigate the problems, such as multi-path effect due to different wireless transmission distance, existing in the large capacity fiber-wireless integration system. We experimentally demonstrate these problems can be effectively solved by advanced DSP algorithms including classic CMA.
KEYWORDS: Digital signal processing, Receivers, Polarization, Transmitters, Heterodyning, Modulation, Radio optics, Antennas, Signal detection, Modulators
In this invited paper, we experimentally demonstrate a seamlessly integrated fiber-wireless system that delivers 108-Gb/s
signal through 80-km fiber and 1-m wireless transport over free-space at 100 GHz, adopting polarization-divisionmultiplexing
quadrature-phase-shift-keying (PDM-QPSK) modulation and heterodyning coherent detection. The X- and
Y-polarization baseband components of the optical PDM-QPSK are simultaneously up-converted to 100-GHz wireless
carriers by optical polarization-diversity heterodyne beating, and then independently transmitted and received by two
pairs of transmitter and receiver antennas, which forms a 2x2 multiple-input multiple-output (MIMO) wireless link. At
the wireless receiver, two-stage down conversion is performed with firstly done in analog domain based on balanced
mixer and sinusoidal radio frequency (RF) signal, and then in digital domain based on digital signal processing (DSP).
MIMO signal de-multiplexing combined with optical polarization multiplexing and free space MIMO crosstalk is
realized by constant modulus algorithm (CMA) in digital signal processing (DSP) part at the receiver. The bit-error ratio
(BER) for the 108-Gb/s PDM-QPSK signal is less than the pre-forward-error-correction (pre-FEC) threshold of 3.8x10-3
after both 1-m wireless delivery at 100 GHz and 80-km single-mode fiber-28 (SMF-28) transmission. To our knowledge,
this is the first demonstration to realize 100-Gb/s signal delivery through both fiber and wireless links at 100GHz.
KEYWORDS: Orthogonal frequency division multiplexing, Signal detection, Receivers, Modulation, Signal attenuation, Signal processing, Optical engineering, Modulators, Optical amplifiers, Dispersion
We experimentally investigate the effect of pilot power allocation on the performance of baseband direct-detected optical orthogonal frequency division multiplexing system by comparing five pilot power allocation schemes. The results show that the scheme of increased pilot power allocation had the highest receiver sensitivity and frequency fading tolerance of all. Allocating more power on pilots at higher frequencies can improve the accuracy of channel estimation which leads to a better system performance.
For the first time, we propose and demonstrate a novel three-level Signal allocation scheme OFDM PON architecture
which makes the best use of OFDM characteristics. In the architecture, we produce five-carrier signal optically by MZM,
use odd carriers modulating downlink data and retain even carriers for uplink data. Multiple signal distribution methods
can be switched flexibly. By simulation, a small PON systems with four ONU based on this architecture was realized.
Both the downlink and uplink transmission adopt 4-QAM-OFDM signal. The transmission rate will be demonstrated to
exceed 10Gbit/s.
In this paper, we propose a single sideband RoF system using high spectrum efficiency MSK modulation. In the system,
one sideband of terahertz wave (THz-wave) undergoes the single sideband MSK modulation while the terahertz wave is
obtained via carrier-suppression double sideband modulation. The BER performance achieves 1x10-9 and the sensitivity
of the receiver is -17.8dBm with a data rate of 5Gb/s after 40km transmission.
KEYWORDS: Tolerancing, Transmitters, Receivers, Modulation, Radio over Fiber, Signal detection, Telecommunications, Single sideband modulation, Phase shift keying, Signal to noise ratio
We propose and simulate a single-side band (SSB) Radio-over-Fiber ( RoF ) system based on OFDM-MSK
modulation. In-phase/quadrature-phase (IQ) imbalance effect can significantly degrade the system performance. In
order to obtain a better system performance, at the transmitter, the phase departure tolerance should be within 1 degree
and the amplitude departure tolerance should be within 5% in the electrical domain, the phase departure tolerance should
be within 10 degrees and the amplitude departure tolerance should be within 40% in the optical domain, the departure
tolerance of splitting ratio should be within ±12%, and at the same time, time misalignment should be within ±32ps. At
the receiver, the phase departure tolerance should be within 2 degrees and the amplitude departure tolerance should be
within 10%. Furthermore, it's further found that the electrical part of the transmitter presents a stricter requirement on the
IQ balance than the receiver, while the receiver presents a stricter requirement on the IQ balance than the optical part of
the transmitter.
We propose algorithm to compensate frequency offset in optical coherent MSK system with little computation
requirement. Simulations are performed to demonstrate the algorithm and its performance is excellent.
KEYWORDS: Single sideband modulation, Double sideband modulation, Receivers, Modulation, Transmitters, Tolerancing, Orthogonal frequency division multiplexing, Telecommunications, Signal detection, Systems modeling
In-phase/quadrature-phase (IQ) imbalance can result in severe performance degradation in optical direct-detection
orthogonal-frequency-division-multiplexing (DD-OFDM) systems. We build two optical back-to-back DD-OFDM
systems, which implement double-sideband (DSB) and single-sideband (SSB) modulation, respectively. The tolerance to
IQ imbalance of these two systems is analyzed and compared using error vector magnitude (EVM) and symbol error rate
(SER). We find that, in the back-to-back case, the DSB system has stronger robustness to IQ imbalance than the SSB
System. We further build two optical DD-OFDM systems each with 40-km transmission, which respectively implement
DSB and SSB transmission. Similarly, we analyze and compare the tolerance to IQ imbalance of these two systems in
terms of EVM and SER. We find that, however, in the case of 40-km transmission, the SSB system has stronger
robustness to IQ imbalance than the DSB system. As a result, we conclude that, in the case of transmission, SSB
modulation can enhance the tolerance to IQ imbalance of DD-OFDM systems.
In this paper, a dual-stage optical single sideband (DSSB) modulation scheme to combat chromatic dispersion for the
terahertz wave over fiber (ToF) systems application is proposed. In the scheme, terahertz(THz) wave is obtained via
carrier-suppression double sideband modulation, one sideband of terahertz wave then undergo the first single sideband
modulation and the second base band SSB modulation in the process of data modulation, which achieves cascade single
sideband (SSB) modulation. As can been seen from the simulation result, for mid-frequency carrier of 0.1THz, the BER
performance without dispersion compensation achieves 1x10-11 and the sensitivity of the receiver is -26.6dBm with a
data rate of 5Gb/s after 100km transmission. Through comparing the power penalty of double side band (DSB) and
DSSB, we demonstrated the optical DSSB modulation has better dispersion tolerance. This paper also shows the
contrastive curves of frequency selective fading for the SSB and DSB modulated signals, which definitely demonstrates
the existence of dispersion fading during the DSB transmission as well as the effective suppression of the fading
implemented by the SSB modulation. The novel scheme's preference is excelled than the conventional scheme's, which
is demonstrated by these theory and simulation.
A WDM PON(wavelength-division-multiplexed passive optical network) structure using 40Gb/s FSK signal for
downstream transmission and 10Gb/s orthogonal FSK/ASK re-modulated signal for upstream transmission is
demonstrated. In the downstream direction, a novel FSK modulation scheme based on phase-to-intensity
modulation conversion is adopted to generate a FSK signal at 40Gb/s, while orthogonal modulation format is used
in the upstream transmission. The performance of the system is studied both with and without scattering. Simulation
results show that the PON system can transmit for more than 20km, which is a promising candidate for future highspeed
access network.
We propose and experimentally demonstrate a novel architecture for OFDM-PON system. The down link is based on
single side band OFDM modulation while the up link makes use of the carrier information retained in another side band
to intensity modulate the data. The downstream transmission will be demonstrated experimentally to exceed 10Gb/s
using 4-QAM while the upstream transmission will exceed 2.5-Gb/s using ASK modulation and Time Division Multiple
Access (TDMA). This architecture can perfectly overcome the Rayleigh scattering effect. It has been proved the
transmission for both directions can reach 10km without bit error. And if the scattering effect is considered, the power
penalty will be less than 0.8dB for downlink and 1.8dB for uplink.
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