Polarization Selectivity of the Thin-Metal-Film Plasmon-Assisted Fiber-Optic Polarizer.

The interaction between light and metallic nanostructures leads to many impressive achievements and has a wide range of applications. The thin-metal-film plasmon-assisted fiber-optic polarizer is one of the essential applications. However, the polarization mechanism and the transmitted polarization of the plasmon-assisted polarizer have given rise to controversy over the past decade.

Long-term stability improvement of tunable optoelectronic oscillator using dynamic feedback compensation.

We propose and demonstrate a novel method to improve the long-term stability of the wideband tunable optoelectronic oscillator (OEO) where a dynamic compensation scheme is achieved to offset the parameter variation of the fiber. In our method, a 900 MHz calibration signal transmits in the fiber link of the OEO's feedback loop for establishing a servo system which can extract the time delay of the feedback loop. The time delay varies with the external environment because refractive index and length of the fiber fluctuate with ambient temperature variations.

Linear dissipative soliton in an anomalous-dispersion fiber laser.

We report on the generation of linear dissipative soliton (LDS) from an erbium-doped actively mode-locked fiber laser. We show that depending on the down-chirping effect of quadratic phase modulation, instead of the fiber nonlinear Kerr effect in an all-normal-dispersion (ANDi) cavity, stable LDS can be realized in the linear dissipative system. The DS operation of ANDi laser and LDS operation of anomalous dispersion laser are experimentally investigated and compared, and the formation mechanisms of the DS and LDS are discussed.

Low overhead slipless carrier phase estimation scheme.

Two slipless schemes are compared with application to single carrier 30 Gbaud quadrature phase shift keying (QPSK) system. An equivalent linewidth model considering the phase noise induced by both the laser linewidth and fiber nonlinearity is applied in the performance analysis. The simulation results show that it is possible to mitigate cycle slip (CS) using only 0.

Investigation on Nyquist pulse generation using a single dual-parallel Mach-Zehnder modulator.

The generation of Nyquist pulses with a dual parallel Mach-Zehnder modulator (DPMZM) driven by a single RF signal is demonstrated theoretically and experimentally. A complete theoretical analysis is developed and the limitation of the proposed scheme is also discussed. It is theoretically proved that Nyquist pulses with a spectrum of 5 flat comb lines can be generated using a single DPMZM, which is also verified with simulation.

Stable fiber-optic time transfer by active radio frequency phase locking.

In this Letter we demonstrate a fiber link capable of stable time signal transfer utilizing our active long-distance radio frequency (RF) stabilization technology. Taking advantage of the chromatic dispersion in optical fiber, our scheme compensates dynamically the link delay variation by tuning the optical carrier wavelength to phase lock a round-trip RF reference. Since the time signal and the RF reference are carried by the same optical carrier, a highly stable time transfer is achieved at the same time.

Experimental investigation on multi-dimensional digital predistortion for multi-band radio-over-fiber systems.

The recently-proposed multi-dimensional digital predistortion (DPD) technique is experimentally investigated in terms of nonlinearity order, memory length, oversampling rate, digital-to-analog conversion resolution, carrier frequency dependence and RF input power tolerance, in both directly-modulated and externally-modulated multi-band radio-over-fiber (RoF) systems. Similar characteristics of the multi-dimensional digital predistorter are identified in directly-modulated and externally-modulated RoF systems. The experimental results suggest implementing a memory-free multi-dimensional digital predistorter involving nonlinearity orders up to 5 at 2 × oversampling rate for practical multi-band RoF systems.

Stokes and anti-Stokes differential pulse pair based distributed Brillouin fiber sensor with double-sideband probe wave.

We propose and demonstrate a distributed Brillouin fiber sensor using Stokes and anti-Stokes differential pulse pair based on double- sideband probe wave, in which the two sidebands of probe wave are used to balance the power of two pump pulses. The spatial resolution is determined by the slightly width difference of the two balanced pulses, without Brillouin gain spectrum broadening. The pulses perform gain-loss process in optical field before the probe signal being detected, without any post-processing or extra measurement time.

Phase-conjugation-based fast RF phase stabilization for fiber delivery.

In this paper, we propose a phase-conjugation-based fast radio frequency (RF) phase auto stabilization technique for long-distance fiber delivery. By phase conjugation at the center site, the proposed scheme pre-phase-promotes the RF signal with the shift which is acquired by round-trip transferring another RF whose frequency is half of the one to be sent. Such phase pre-promotion is then used to counteract exactly the following retard induced by one-way delivery.

Multifrequency radio frequency sensing with photonics-assisted spectrum compression.

We propose and demonstrate a multifrequency radio frequency (RF) spectrum estimation technology. With photonic assistance, a multifrequency RF signal ranging from 0 to 1 GHz is highly spectrally compressed and sensed using a single analog-to-digital converter with analog bandwidth of 42.6 MHz.

Intermodulation distortion suppression for intensity-modulated analog fiber-optic link incorporating optical carrier band processing.

An intermodulation distortion suppression method based on the optical carrier band processing is demonstrated. A systematic analysis of the main optical spectrum contributors for the third-order intermodulation distortion in the nonlinear system is presented. Theoretical analysis shows that the third-order intermodulation distortion terms can cancel each other if a proper phase shifting is imposed to the optical carrier band.

Pilot-symbols-aided cycle slip mitigation for DP-16QAM optical communication systems.

A pilot-symbols-aided phase unwrapping (PAPU), which utilizes the time-division multiplexed pilot symbols that are transmitted with data, is proposed to do cycle slip detection and correction with the carrier phase estimation (CPE). Numerical simulations for 10 Gbaud dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) systems show that the block averaging quadrature phase-shift keying (QPSK) partitioning with PAPU greatly eliminates the performance degradation caused by cycle slips, maintains a low CS probability with less influence of filter length, and achieves a bit-error-rate (BER) performance below soft-decision forward error correction (FEC) limit 2 × 10⁻² at 15 dB optical signal-to-noise ratio with only 1.56% overhead and 6 MHz combined laser linewidth.

High-repetition-rate, stretch-lens-based actively-mode-locked femtosecond fiber laser.

We propose and demonstrate a novel actively mode-locked fiber laser based on a stretch-type time-lens. The pulse generated by this scheme has high repetition rate and large bandwidth while no nonlinearity is participated. A 10-GHz chirped pulse train with 18-ps duration and 11.

Performance analysis for IEEE 802.11 distributed coordination function in radio-over-fiber-based distributed antenna systems.

In this paper, we analyze the performance of IEEE 802.11 distributed coordination function in simulcast radio-over-fiber-based distributed antenna systems (RoF-DASs) where multiple remote antenna units (RAUs) are connected to one wireless local-area network (WLAN) access point (AP) with different-length fiber links. We also present an analytical model to evaluate the throughput of the systems in the presence of both the inter-RAU hidden-node problem and fiber-length difference effect.

Non-line-of-sight ultraviolet single-scatter propagation model in random turbulent medium.

Non-line-of-sight (NLOS) ultraviolet communication (UVC) uses the atmosphere as a propagation medium. In previous literature, various scatter propagation models have been derived based on the premise that atmospheric turbulence was ignored and the atmosphere was considered as a turbid medium, also called random scatterers. In this Letter, a NLOS single-scatter propagation model is proposed to describe the singly scattered radiation in a turbulent medium, also called a random continuum, such as the clear atmosphere.

Stable radio-frequency delivery by λ dispersion-induced optical tunable delay.

We propose and demonstrate a novel stable radio frequency (RF) delivery system based on a radio-over-fiber link. The proposed scheme acts as a long phase-locking loop where an optical tunable delay line is involved to compensate dynamically for the time-delay variation that arises from fiber-link fluctuation. An optical carrier with variable wavelength under fiber-link dispersion results in the desired tunable delay.

Closed-form path loss model of non-line-of-sight ultraviolet single-scatter propagation.

Non-line-of-sight ultraviolet propagation models have been developed for both coplanar and noncoplanar geometries. Based on an exact integral-form single-scatter model, this Letter proposes an approximate closed-form model for tractable analysis applicable to noncoplanar geometries with a narrow transmitter beam or receiver field of view. Numerical results on path loss are presented for various system geometries.

Stable radio frequency phase delivery by rapid and endless post error cancellation.

We propose and demonstrate a phase stabilization method for transfer and downconvert radio frequency (RF) signal from remote antenna to center station via a radio-over-fiber (ROF) link. Different from previous phase-locking-loop-based schemes, we post-correct any phase fluctuation by mixing during the downconversion process at the center station. A rapid and endless operation is predicted.

Complexity-reduced digital predistortion for subcarrier multiplexed radio over fiber systems transmitting sparse multi-band RF signals.

A novel multi-band digital predistortion (DPD) technique is proposed to linearize the subcarrier multiplexed radio-over-fiber (SCM-RoF) system transmitting sparse multi-band RF signal with large blank spectra between the constituent RF bands. DPD performs on the baseband signal of each individual RF band before up-conversion and RF combination. By disregarding the blank spectra, the processing bandwidth of the proposed DPD technique is greatly reduced, which is only determined by the baseband signal bandwidth of each individual RF band, rather than the entire bandwidth of the combined multi-band RF signal.

Ultra-low timing-jitter 40GHz clock recovery using EAM-MZM double-loop and its application in a 640Gbit/s OTDM system.

An ultra-low timing-jitter clock recovery scheme based on EAM-MZM double-loop with the ability of simultaneous time-division demultiplexing is proposed and demonstrated in a 640 Gbit/s OTDM transmission system. Compared with traditional clock recovery scheme based on OEO loop, significant timing-jitter improvement of the 40 GHz recovered clock is realized: from 58 fs to 30 fs in back-to-back configuration and from 59 fs to 35 fs after 400 km transmission in the 100 Hz to 10 MHz range, without increasing the overall system complexity and cost. Enabled by the proposed clock recovery and demultiplexing scheme, error-free performance of the OTDM system is achieved after 400 km transmission with an average power penalty of 4dB.

Nonlinear signal-noise interactions in dispersion managed coherent PM-QPSK systems in the presence of PMD.

Considering the polarization mode dispersion(PMD), the transmission penalty induced by nonlinear signal-noise interactions (NSNI) between the amplified spontaneous emission noise (ASE) and the information signal is investigated numerically for 40(100)G dispersion-managed(DM) polarization-multiplexed quadrature phase-shift keying (PM-QPSK) systems. We show that for single-channel PM-QPSK systems, PMD is helpful to reduce the NSNI-induced penalty. For multi-channel PM-QPSK system, however, the NSNI-induced nonlinear penalty is significantly enhanced by PMD, especially at low bit-rate.

Digital joint compensation of IMD3 and XMD in broadband channelized RF photonic link.

Based on forward distortion information acquisition and post digital signal processing (DSP), we propose and demonstrate a novel scheme to effectively suppress the third-order intermodulation distortion (IMD3) and cross-modulation distortion (XMD) in a channelized RF photonic link. The simultaneous distortion compensation capacity is studied numerically, and suppression of XMD and IMD3 by about 28 dB and 25 dB, respectively, is achieved experimentally. The scheme principle and the digital compensation procedure are discussed, which shows a simple hardware implementation and algorithm.

Generation and performance Investigation of 40GHz phase stable and pulse width-tunable optical time window based on a DPMZM.

We experimental demonstrate stable, simple and pulse width-tunable 40 GHz short time window generation using a dual parallel Mach-Zehnder modulator (DPMZM) driven simply by an electrical clock. The pulse widths are measured to be tunable continuously from 5.6 ps to 12.

Bit-error-rate performance of non-line-of-sight UV transmission with spatial diversity reception.

In non-line-of-sight (NLOS) UV communication links using intensity modulation with direct detection, atmospheric turbulence-induced intensity fluctuations can significantly impair link performance. To mitigate turbulence-induced fading and, therefore, to improve the bit error rate (BER) performance, spatial diversity reception can be used over NLOS UV links, which involves the deployment of multiple receivers. The maximum-likelihood (ML) spatial diversity scheme is derived for spatially correlated NLOS UV links, and the influence of various fading correlation at different receivers on the BER performance is investigated.

A single-scatter path loss model for non-line-of-sight ultraviolet channels.

In this paper, a novel single-scatter path loss model is presented for non-line-of-sight (NLOS) ultraviolet (UV) channels. This model is developed based on the spherical coordinate system and extends the previous restricted models to handle the general noncoplanar case of arbitrarily pointing transmitter and receiver. Numerical examples on path loss are illustrated for various system geometries.