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Coherent optical receivers have been widely used in free-space optical communication. We report on a coherent receiver with a homodyne optical phase-locked loop using a Costas loop. Differing from the conventional configuration, the demonstration in this paper with enhanced dynamic performance using an auxiliary acquisition and locking circuitry is able to achieve fast phase locking to signal laser...
In this paper, a free-space optical (FSO) communication system with supercontinuum source generated by dispersion shift fiber (DSF) from pulsed light modulated by optical switches is designed and constructed. In addition, the experimental results of free-space optical communication between broadband and narrowband light source are compared. Verifying the feasibility of broad-spectrum FSO communication...
A regional fault-tolerant restoration mechanism based on SDN is proposed for fiber communication networks. Simulation results show that this mechanism has shorter recovery time and lower restoration failure rate than other mechanism because of avoiding the occurrence of regional faults.
A challenge is to measure the impairments of few-mode fiber (FMF) for mode division multiplexing (MDM) system, so as to quantify the few-mode fiber and compensate the impairments, and thus improves the transmission performance of MDM system. In this paper, the experimental setup of impairments measurement with the structure of Photonic Lantern and optical circulators is established. Not only the two...
An in-line Mach-Zehnder interferometric refractive index (RI) sensor is demonstrated by concatenating two single-mode fiber (SMF) half-tapers separated by one section of SMF. The cladding modes excited at the first half-taper interferes with the core mode at the second half-taper to generate the interference fringe. Theoretical and experimental results consistently show that the interference fringe...
A multiwavelength random fiber laser based on stimulated Brillouin scattering (SBS) with odd and even order Stokes output separated is proposed and demonstrated experimentally. The gain is provided by the SBS and erbium doped fiber amplifier, while the Rayleigh scattering in single mode fiber (SMF) provides random distributed feedback. With a two-branch structure, we successfully make the laser output...
We have investigated L-band dispersion-managed mode-locked (DMML) fiber laser incorporating carbon-nanotube saturable absorbers. For the first time, the DMML fiber laser operates at 1595 nm with the net cavity dispersion changing from −0.34 to −0.20 ps2, showing that the spectral bandwidth can be broadened by 39%.
An all-optical multilevel amplitude regenerator is optimized based on the transmission response of a nonlinear optical loop mirror (NOLM). Three regenerative regions defined by the power-transfer-function (PTF) slope of less than 1 are obtained, and noise suppression is shown for a PAM4 signal. Using amplitude dithering we were able to experimentally characterize the transfer function slope and confirm...
In-fiber gratings provide a perfect platform for directly processing optical signals in optical fiber with ultra fast speed. Their spectral profile and dispersion profile can tailored to realise various functionalities in different applications. This paper will focus on the discussion of our past and recent development on fiber grating devices that are used for optical signal processing.
In this paper we demonstrate the 4 level pulse amplitude modulation (PAM-4) signal generation through a silicon Mach-Zehnder modulator. The baud speed of the PAM-4 signal generation is characterized up to 32 Gbaud (64Gb/s). And we have measured the device's bit error rate (BER) up to 32 Gbaud and the spurious free dynamic range (SFDR) of the distortion component of the modulated light.
By an orchestra of multiple enabling techniques at the transmitter and receiver, we experimentally demonstrate a single-channel 102.4-Gb/s transmission up to 240-km standard single-mode fiber (SSMF) at C-band with direct detection. At the transmitter, we realize Nyquist-pulse shaping PAM-4 (NPAM-4) modulation and single-sideband modulation by using a dual-drive Mach-Zehnder modulator. At the receiver,...
In this paper, wavelength division multiplexing and space division multiplexing (WDM-SDM) passive optical access network employing multi-core fiber (MCF) and self-homodyne detection is proposed. 4×56-Gb/s PDM-16QAM-OFDM transmission is realized over 10-km 7-core fiber with simplified digital signal processing.
In this paper, a 60cm free-space optical card-to-card wavelength division multiplexing (WDM) transmission architecture using OFDM modulation and coherent detection is proposed and demonstrated, which can offer flexibility and high speed transmission simultaneously. The experimental results show that the net data rate is up to 106.9Gb/s and the receiver sensitivity is −34dBm at the BER threshold of...
The sensing performance in Brillouin-based distributed fiber sensors is ultimately depends on the signal-to-noise ratio (SNR) of the received signal. In order to enhance the SNR, thus improve the sensing performance, several wavelength diversity techniques have been proposed. This paper presents the current wavelength diversity techniques employed in both Brillouin optical time-domain reflectometry...
Ballistocardiography (BCG) is a non-invasive method for measuring the reaction force of the human body to the ejection of blood at each cardiac cycle. It is now being the subject of renewed research interest due to recent technological advancement in the field of sensors. In this paper, we summarize our work on BCG with optical fiber sensors for various applications in the past 6 years. These include...
Ballistocardiography (BCG) is a non-invasive method for measuring the reaction force of the human body to the ejection of blood at each cardiac cycle. It is now being the subject of renewed research interest due to recent technological advancement in the field of sensors. In this paper, we summarize our work on BCG with optical fiber sensors for various applications in the past 6 years. These include...
Weight distribution of code is very important for error correction in the use of Turbo coding program in optical fiber communication. Input sequence need to pass convolutional encoder, Therefore, it is necessary that the weight of the output should be kept as large as possible. Although the interleaver can help to improve the output code weight, the higher the complexity of interleaving, the iterative...
We experimentally demonstrate the high-speed free-space optical (FSO) transmission over 1 km using 20 Gbit/s advanced coherent quadrature phase-shift keying (QPSK) signals. The constellation diagram and the bit error rate (BER) are measured. The receiving sensitivity of the FSO transmission is about −23.9 dBm at the BER of 3.3×10−3.
For metro applications, direct detection offers the advantages of low cost and low complexity. Discrete multi-tone (DMT) is a promising format due to its high spectral efficiency, flexibility and tolerance to chromatic dispersion (CD). In this work, single-side-band-DMT (SSB-DMT) and tuneable electrical dispersion compensation double side-band-DMT (TEDC-DSB-DMT) are summarized and compared.
We demonstrated femtosecond laser inscription of fiber Bragg gratings (FBGs) in a twin-core few-mode fiber (TC-FMF) for directional bend sensing. An FBG was selectively inscribed in one core of the TC-FMF by using an 800 nm femtosecond laser through a phase mask. Three resonance peaks at the wavelengths of 1549.05, 1547.65, and 1546.08 nm were observed in the reflection spectrum of the TC-FM FBG,...
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