10-GHz 0.5-ps Pulse Generation in 1000-nm Band in PCF for High-Speed Optical Communication

We achieved the first 10-GHz subpicosecond pulses in the 1000-nm band by employing the higher order soliton effect in a 190-m photonic crystal fiber (PCF). We obtained 0.5-ps pulses at 1063 nm by compressing 11-ps pulses from a harmonically mode-locked Yb fiber laser with a 10-GHz repetition rate, which was stabilized with phase-locked-loop technology. This light source is attractive in terms of realizing a hundreds-of-gigabits-per-second optical-time-division-multiplexing transmission over a low-loss PCF in the 1000-nm band     

A 40-GHz 0.9-ps regeneratively mode-locked fiber laser with atuning range of 1530-1560 nm

A stable 40-GHz pulse train was successfully generated from a regeneratively mode-locked fiber laser. The laser was locked to an external signal by a phase-locked loop (PLL) technique. The output pulsewidth was as short as 0.9 ps using a soliton effect in the fiber cavity and the wavelength was tunable between 1530 and 1560 nm     

Supermode stabilized coupled-cavity 5- and 10-GHz mode-lockedTi:Er:LiNbO3 waveguide lasers

By coupling the active laser cavity to a passive low-finesse Fabry-Perot resonator, supermode stabilization of mode-locked Ti:Er:LiNbO₃ waveguide lasers for 5- and 10-GHz pulse repetition rates with side mode suppression ratios of 60 and 55 dB has been achieved. The 10-GHz source emits pulses with a pulsewidth of 5.7 ps and a time-bandwidth product lower than 0.52 within an RF frequency tuning range of 3.2 MHz. The 5-GHz source has been used in a 2×5 Gbit/s soliton transmitter. In a back-to-back measurement, a Q-factor of 25.1 dB has been obtained. In soliton transmission experiments over 160 km on a step-index fiber, an extrapolated bit error rate of 6·10 ^-17 has been measured. The passive cavity can serve also as a pulse repetition rate multiplier. Pulse repetition rate multiplication from 2.5 to 10 GHz has been demonstrated     

High-power widely tunable 40-GHz pulse source for 160-gb/s OTDM systems based on nonlinear fiber effects

We numerically analyze and experimentally demonstrate an innovative and simple 40-GHz source for 160-Gb/s optical time-division multiplexing. The source is based on nonlinear evolution of a sine-modulated lightwave in a Raman-pumped fiber. Proper nonlinear propagation produces the simultaneous soliton generation and compression. High-power soliton-like pulses are obtained with <1-ps pulsewidth. The source can be tuned over 20 nm and it has more than 100-mW average output power.     

100-GHz soliton pulse train generation using soliton compression oftwo phase side bands from a single DFB laser

A 100-GHz soliton pulse train, with the potential of very low timing jitter, is generated using soliton compression of the beat signal between two optical carriers. The optical carriers are obtained by optically filtering out the third-order sidebands generated from a single DFB laser and a LiNbO₃ electro-optic phase modulator driven at 16.9 GHz     

40-GHz pulse train generation using soliton compression of aMach-Zehnder modulator output

We demonstrate 40-GHz soliton pulse train generation using nonlinear compression of the output of a Mach-Zehnder modulator. This source generates transform-limited pulses at twice the RF drive frequency, requires less than V_π drive level, is tunable in wavelength (over the entire EDFA bandwidth), and is tunable in repetition rate     

80-GHz pulse generation from a repetition-rate-doubled FM mode-locking fiber laser

We demonstrated a simple method to realize repetition-rate-doubling in a frequency modulation (FM) mode-locking fiber laser. The mode-locking of the laser is based on converting FM modulation to amplitude modulation by using a phase-modulated optical fiber loop mirror, which is formed by a phase modulator and an additional coupler only. With 40-GHz modulation, we obtained 80-GHz 1.74-ps transform-limited pulse train in the experiments.     

An Impulse System for 60-GHz Wireless Networks Based on Polymer Optical Fiber

A specific impulse optical fiber system has been achieved to enhance the connectivity of 60-GHz wireless networks. Using an impulse technology, this original configuration is an efficient alternative to the conventional 60-GHz radio-over-fiber systems. Baseband subnanosecond pulses first modulate the amplitude of a 60-GHz radio-frequency carrier and second the intensity of a distributed feedback laser operating at 1300 nm. Properties of the multimode plastic optical fiber based on a perfluorinated material are exploited to transmit such signals. The overall system performance has been tested experimentally in a multihop configuration; bit-error-rate measurements are better than for transmission data rates up to 200 Mb/s.     

Low-jitter and high-power 40-GHz all-active mode-locked lasers

A novel design strategy for the epitaxial structure of monolithic mode-locked semiconductor lasers is presented. Using an all-active design, we fabricate 40-GHz lasers generating 2.8-ps almost chirp-free pulses with record low high-frequency jitter and more than 7-mW fiber coupled output power.     

Multiband Signal Generation and Dispersion-Tolerant Transmission Based on Photonic Frequency Tripling Technology for 60-GHz Radio-Over-Fiber Systems

We designed and experimentally demonstrated an efficient photonic frequency-tripling technology for 60-GHz radio-over-fiber systems to simultaneously realize millimeter-wave (mm-wave), microwave, and baseband signal generation. The technique utilizes vestigial sideband filtering in combination with optical carrier suppression to generate novel alternate subcarrier modulation for high tolerance of fiber dispersion. Experimental verification of the proposed scheme is presented with generation and error-free transmission of 2.1-Gb/s data on the 63-GHz mm-wave and 21-GHz microwave carriers over 50-km single-mode fiber (SMF-28) without dispersion compensation. The power penalty for both signals is less than 1.0 dB.      

40-GHz transform-limited pulse generation from FM oscillation fiber laser with external cavity chirp compensation

A 40-GHz frequency modulation oscillation fiber laser is demonstrated and the continuous-wave (CW) output is used for generating a high repetition rate short pulse train by external cavity chirp compensation. A 1.37-ps transform-limited pulse is obtained from its chirped, 488.1-GHz width CW output.     

Stabilized Phase-Modulated Rational Harmonic Mode-Locking Soliton Fiber Laser

We realized the repetition rate multiplication in a phase-modulated soliton fiber laser with the rational harmonic mode-locking method. A modified pulse phase-locking method is used to stabilize the fiber laser at 10-GHz repetition rate with the rational harmonic order up to five (limited by the component performance). The laser showed an excellent stabilization performance in a long-term bit-error-rate test     

New optical microwave up-conversion solution in radio-over-fiber networks for 60-GHz wireless applications

A new method for generating optical microwave mixing based on the optical phase modulation and the fiber chromatic dispersion is further investigated. A theoretical approach based on the analysis of the optical field spectrum has lead to the evaluation of the mixing power and optimal fiber lengths of 60-GHz radio-over-fiber (RoF) networks. Results have shown adaptable fiber lengths to match the network specifications.     

Ultralong dispersion-shifted erbium-doped fiber amplifier and itsapplication to soliton transmission

Distributed, dispersion-shifted erbium-doped fiber amplifiers with doping concentrations as low as 0.1-0.5 p.p.m. (0.1-0.5×10^-4 wt.%) were fabricated and their grain characteristics studied for the purpose of soliton amplification. A 9.4-km dual-shape-core-type amplifier with a 0.5-p.p.m. concentration had a gain of more than 20 dB at 1.535 μm and 10 dB at 1.552 μm with a forward pumping configuration, and it could successfully amplify and transmit a 20-ps soliton pulse train at a 2.5-GHz repetition rate. The soliton transmission characteristics of an 18.2 km long fiber amplifier were studied using backward and forward pumping. It was found that A=1.5 soliton pulses with a pulse width of 20 ps could be amplified over 18.2 km at a repetition rate of 5 GHz, where soliton narrowing to 16 ps was observed     

A 24-GHz Ultra-Wideband Over Fiber System Using Photonic Generation and Frequency Up-Conversion

We propose and experimentally demonstrate the generation of baseband ultra-wideband (UWB) monocycle and doublet pulses using one dual-parallel Mach–Zehnder modulator. We further present a proof-of-concept demonstration of a 24-GHz UWB over fiber system based on frequency up-conversion. The performance of the up-converted UWB pulses after fiber transmission is studied.      

10-GHz and 20-GHz Channel Spacing High-Resolution AWGs on InP

This letter reports on 10-GHz and 20-GHz channel-spacing arrayed waveguide gratings (AWGs) based on InP technology. The dimensions of the AWGs are 6.8$,times,$8.2 mm$^{2}$ and 5.0$,times,$6.0 mm$^{2}$, respectively, and the devices show crosstalk levels of $-$12 dB for the 10-GHz and $-$17 dB for the 20-GHz AWG without any compensation for the phase errors in the arrayed waveguides. The root-mean-square phase errors for the center arrayed waveguides were characterized by using an optical vector network analyzer, and are 18 $^{circ}$ for the 10-GHz AWG and 28$^{circ}$ for the 10-GHz AWG.      

165-GHz Transceiver in SiGe Technology

Two D-band transceivers, with and without amplifiers and static frequency divider, transmitting simultaneously in the 80-GHz and 160-GHz bands, are fabricated in SiGe HBT technology. The transceivers feature an 80-GHz quadrature Colpitts oscillator with differential outputs at 160 GHz, a double-balanced Gilbert-cell mixer, 170-GHz amplifiers and broadband 70-GHz to 180-GHz vertically stacked transformers for single-ended to differential conversion. For the transceiver with amplifiers and static frequency divider, which marks the highest level of integration above 100 GHz in silicon, the peak differential down-conversion gain is -3 dB for RF inputs at 165 GHz. The single-ended, 165-GHz transmitter output generates -3.5 dBm, while the 82.5-GHz differential output power is +2.5 dBm. This transceiver occupies 840 mum times 1365 mum, is biased from 3.3 V, and consumes 0.9 W. Two stand-alone 5-stage amplifiers, centered at 140 GHz and 170 GHz, were also fabricated showing 17 dB and 15 dB gain at 140 GHz and 170 GHz, respectively. The saturated output power of the amplifiers is +1 dBm at 130 GHz and 0 dBm at 165 GHz. All circuits were characterized over temperature up to 125degC. These results demonstrate for the first time the feasibility of SiGe BiCMOS technology for circuits in the 100-180-GHz range.     

Combined single-mode/multimode fiber link supporting simplified in-building 60-GHz gigabit wireless access

In this paper, we propose and experimentally demonstrate a simple, cost-effective hybrid gigabit fiber-wireless system for in-building wireless access. Simplicity and cost-effectiveness are achieved in all parts of the system by utilizing direct laser modulation, optical frequency up-conversion, combined single mode/multimode fiber transmission and envelope detection. Error-free transmission of 2-Gbps data in 60-GHz band over a composite channel including 10-km standard single-mode fiber (SSMF)/1-km multimode fiber (MMF) and 6.5-m air transmission was successfully achieved.     

Multi-band QPSK signal transmission implemented with remote up-conversion and Schottky RF detectors in a 60-GHz millimeter wave radio-over-fiber system

A simple multi-band QPSK signal transmission scheme, constructed by using an optical remote up-conversion technique and a Schottky diode RF detector, is theoretically analyzed and experimentally implemented in a 60-GHz millimeter wave (mm-wave) radio over fiber (RoF) system, for the first time. There is no need for complex system architecture or any expensive high-frequency clock source in our scheme. Simulation results show that our scheme is highly tolerant to fiber dispersion, compared with the conventional 60 GHz multi-band RoF system. In the experimental demonstration, successful delivery of QPSK signals at two 60-GHz sub-bands is achieved over 50-km fiber and 4-m wireless distance.     

80-160-GHz mode-locked fiber ring laser synchronized to external optical pulse stream

The authors present a novel scheme to generate ultrahigh repetition rate picosecond pulses synchronized to an optical pulse stream in an actively mode-locked fiber ring laser. A monolithic Mach-Zehnder interferometer with integrated semiconductor optical amplifiers serves as an 80-GHz optically controlled modulator. 80-GHz transform-limited 2.1-ps Gaussian pulse with low timing jitter, extinction ratios up to 25 dB, and 5 mW of average output power are demonstrated. The laser is wavelength tunable over more than 15 nm around 1555 nm. At 160 GHz, 2.5-ps pulse trains with 3-mW output power are generated by rational harmonic mode locking.