The use of photonic systems to address the demands of high speed signal processing has grown swiftly in the past few years. One current photonic technology that has been extensively researched for analog and digital applications is the Optoelectronic Oscillator, often referred to as an OEO [1]. The OEO was first introduced by Yao and Maleki [2, 3] in 1996 as a source for high frequency, low phase noise signals. Since the OEO provides high performance with the use of commercial parts that are inexpensive, multiple demonstrations have been made both improving and extending the initial design. In fact the OEO has been used for far more than just signal generation. A couple of applications that have received a large amount of attention are clock recovery and signal discrimination. This paper will review the multiple advancements in OEOs for these applications.

The maturity of RF photonic components has reached the point where fiber optic links are being system tested to replace traditional copper coax links on avionic platforms. Many demonstrations of RF photonic links have been made with traditional and non-traditional modulation formats [1-4] to improve the RF performance of the link. While the advantages of RF photonic links in regard to size and weight are indeed important, the large instantaneous bandwidth of the fiber optic links is a key driver for the use of this technology in the airframe. As signals of interest evolve to higher frequencies, the use of RF photonics provides a path to identify and catalog these new signals. With the acceptance of the fiber optic link as a replacement to coax, the next step is to move the photonic technology to provide signal processing capability in the optical domain before converting back to an electrical signal. The current challenges are to continue to explore new photonic technologies for improved RF performance at the receive end of the link. This paper will focus on advancements in RF photonic solutions for signal processing.

Employing all-optical means to prepare phase-coherent input signal-idler pairs, we implement a multichannel in-line phase-sensitive fiber-parametric amplifier. Feasibility of three-channel operation using a single pump is demonstrated.

We demonstrate an optoelectronic oscillator using a gain-switched vertical-cavity surface-emitting laser in a fiber-feedback configuration. We simultaneously generate a 2-GHz optical pulse stream at 850 nm with 750-fs timing jitter (over 100 Hz-10 MHz range) along with an electrical signal that is locked to the repetition rate of the optical pulses. The timing jitter performance is confirmed by measuring higher harmonic phase noise.

A theoretical analysis and an experimental demonstration of semiconductor optical amplifier (SOA)-based regenerative amplification (SORA) of phase noise (PN)-degraded return-to-zero (RZ) differential phase-shift keying (DPSK) signals are presented. The Q-factor improvement is 1.6 dB in single-channel and about 0.8 dB in two non-demultiplexed-channel regimes. The key physical mechanism that enables regeneration by the SORA is the discriminative gain provided by the SOA for the logical 0s versus the logical 1s when two mutually antisymmetric ON-OFF keying (OOK) data trains, created by the DPSK signal, collide in the SOA. The modeling results agree with the experiment.

We demonstrate a phase-sensitive fiber-optical parametric amplifier based on frequency-nondegenerate four-wave mixing in the telecom band. An input signal is phase-sensitively amplified and the measured gain response complies well with the theory. Efficient phase-sensitive amplification can be achieved even after transmitting an optical double-sideband signal over 25 km of single-mode fiber.

We demonstrate the first fiber-optic phase-sensitive parametric amplifier based on frequency-nondegenerate four-wave mixing. An input signal is phase-sensitively amplified and the measured gain response matches well with the theory.

We demonstrate simultaneous wavelength conversion of multiple DPSK channels using four-wave mixing in highly-nonlinear fiber. We achieve 20 nm converter bandwidth with 85% maximum efficiency. Three 10 Gb/s channels are converted without cross-modulation penalty

Presented is dynamic analysis for SOA-based regenerative amplification (SORA) of phase-noise-degraded DPSK signals, which led to the first recent practical demonstration of a SORA. The modelling results agree with the experiment. The regeneration is achieved without wavelength conversion and/or using additional laser resources.

Error-free transmission of 2.5 Gbit/s data over 60 km of dispersion compensated standard single-mode fibre is demonstrated by using an inline phase-sensitive fibre-parametric amplifier and double-sideband data modulation format. The power penalty for the phase-sensitive amplifier was found to be < 0.5 dB compared to back-to-back for bit-error-rate > 10(-6) and < 2 dB compared to that for an equivalent phase-insensitive fibre-parametric amplifier of the same gain.

The parametric scattering / four-wave mixing process in optical fibers can be utilized for various quantum (entanglement generation) and classical (signal amplification) communication applications. This talk will present our recent developments in this field.

We demonstrate clock recovery with ultralow timing jitter by using a novel self-starting optoelectronic oscillator that is based on an electroabsorption modulator in a fiber extended cavity. The oscillator simultaneously generates a 10-GHz-rate microwave signal and a train of 15-ps optical pulses with /spl sim/40-fs timing jitter in the 100-Hz to 1-MHz range. Under direct optical-injection locking of the oscillator, we demonstrate simultaneous error-free extraction of both the electrical and the optical clocks of 10-GHz rate from either a single-channel 10-Gb/s return-to-zero data stream or a four-channel 40-Gb/s optical time-division-multiplexed data stream.

Recent theoretical work predicts that the quantum-limited noise figure of a x(3)-based fiber-optical parametric amplifier operating as a phase-insensitive in-line amplifier or as a wavelength converter exceeds the standard 3-dB limit at high gain. The degradation of the noise figure is caused by the excess noise added by the unavoidable Raman gain and loss occurring at the signal and the converted wavelengths. We present detailed experimental evidence in support of this theory through measurements of the gain and noise-figure spectra for phase-insensitive parametric amplification and wavelength conversion in a continuous-wave amplifier made from 4.4 km of dispersion-shifted fiber. The theory is also extended to include the effect of distributed linear loss on the noise figure of such a long-length parametric amplifier and wavelength converter.

A self-starting regeneratively modelocked fibre-optical parametric oscillator that utilises four-wave mixing in a highly nonlinear fibre together with intra-cavity soliton formation to generate tunable, dual-wavelength picosecond pulses at 10 GHz rate simultaneously in the C- and L-bands, is demonstrated, believably for the first time. An electroabsorption-modulator-based optoelectronic oscillator is used as an ultra-low-jitter pump source that enables, by means of direct feedback injection locking, a significant reduction of the timing jitter of the obtained pulses.

We demonstrate a novel, polarization-insensitive scheme for multiwavelength nonreturn-to-zero to return-to-zero format conversion at 10 Gb/s rate with significant timing-jitter suppression and signal-to-noise ratio improvement. The scheme utilizes a self-starting electroabsorption-modulator based optoelectronic oscillator that simultaneously generates a 10 GHz-rate microwave signal and a train of 15 ps-wide optical pulses with ∼40 fs timing jitter (100–10 MHz range). Under direct optical injection locking of the oscillator with an incoming data stream, we demonstrate the extraction of a high-quality clock that enables in-line format conversion of multiple, synchronized nonreturn-to-zero channels.

We demonstrate a novel, polarization-insensitive scheme for multiwavelength NRZ-to-RZ conversion at 10 Gb/s rate with significant timing jitter suppression. It utilizes an electroabsorption-modulator based optoelectronic oscillator for high quality clock recovery.

We demonstrate a microstructure-fiber (MF)-based supercontinuum source and a synchronously pumped optical parametric oscillator in the 1550-nm regime. By using a 12.5-m-long MF, we obtained a 10-GHz repetition-rate picosecond-pulse source that is capable of similar to120-nm wavelength tunability due to the wide-gain bandwidth of the combined processes of stimulated Raman scattering and parametric four-wave mixing.

We demonstrate, for the first time to our knowledge, a telecom-band optical parametric amplifier made with microstructure fiber. Preliminary measurements yield signal gain >15 dB over ∼20 nm range around 1550 nm using only 23 m of fiber.

We demonstrate a microstructure-fiber based supercontinuum source and an optical parametric oscillator in the 1550nm regime. By using only 12.5m-long fiber, we obtained a 10GHz repetition rate picosecond pulse source capable of -120nm wavelength tunability. 02002 Optical Society of America OCIS codes: (060.2320) Fiber optics, amplifiers and oscillators; (060.4370) Nonlinear optics, fibers Microstructure Fibers (MFs) have attracted considerable attention owing to their high nonlinearity per unit length. All nonlinear effects present in standard optical fibers should be observable in MFs with reduced length and pumppower requirements. Thus far, almost all demonstrations of the nonlinear optical processes using MFs have been in the visible region of the optical spectrum. These include four-wave mixing’ (FWM), supercontinuum generation2 (SCG), and optical parametric oscillation3 (OPO). Here we report on the SCG using a telecom-band pump source, leading to the operation of a 10-GHz repetition-rate synchronously pumped microstructure-fiber optical parametric oscillator (MFOPO) with 30nm demonstrated tunability and with potential for over 120nm of tunability in the 1550nm telecom regime. A schematic of the experimental setup appears in Fig. 1. The 12.5m-long piece of MF was fabricated at CrystalFibre A/S4 The silica core of this fiber has an average diameter of 2.4 (+/-0.2) pm, whch is surmunded by a hexagoid array of approximately 0.8p-diameter air voids, and the zero-dispersion wavelength is b=1544 (+/-3) nm. The MFOPO is configured as a ring cavity in which a tunable optical bandpass filter (OBF) selects the desired oscillating wavelength. The 5.9ps pump pulses are obtained from a mode-locked fiber laser operating at lOGHz repetition rate with &=1537nm. After amplification by a high-power EDFA the pump is coupled into the ring cavity using a bandpass wavelength-division multiplexer (BWDM). When the fiber loop is open (Le., point A is disconnected from the MF), supercontinuum is generated in the MF. When the loop is closed and the pump repetition rate is adjusted equal to an integer multiple of the cavity free-spectral range, synchronous MFOPO action is established. Figure 2 shows the open-loop supercontinuum spectra for various launch powers into the MF, where for 5.9W pump peak power the 30dB (relative to the pump) bandwidth of the continuum is 120nm. The closed-loop MFOPO results are shown in Fig. 3, where a composite of the output spectra for five different oscillating signal wavelengths is shown along with the residual pump. The tunability range of the signal wavelength in our setup at present is limited by the characteristics of the OBF and the BWDM. Also shown is the corresponding supercontinuum spectrum for 5.9W of pump peak power, which implies that, with an appropriate OBF and BWDM, the synchronized MFOPO is capable of over 120nm wavelength tunability. The pulse width of the oscillating signai was measured to be 2.2ps with use of an autocorrelator and found to be limited by the 1-nm bandwidth of the OBF. Use of a 3-nm bandwidth filter resulted in <Ips signal pulses. The left inset in Fig. 3 shows an example of the measured oscillating signal peak power as a function of the pump peak power injected into the MF. The oscillation threshold is clearly seen when the pump peak power exceeds 2W. The right inset in Fig. 3 shows an example of the measured FOP0 output spectrum. We believe this widely tunable high-repetition-rate picosecond pulse source would be very useful in high-capacity WDM-TDM transmission systems. We thank Rene Kristiansen of Clystal Fiber A/S for loan of the connectorized MFs. This work was supported by the National Science Foundation under Grants: ANI-

Here, we report on the use of an advanced version of the electroabsorption modulator - optoelectronic oscillator (EAM-OEO) to convert multiple independent CW distributed feedback (DFB) lasers into synchronized 10 GHz-rate optical pulse streams for use in the C, L, and U-bands of the fiber-optic communication spectrum. The generated optical pulse streams have ultra-low jitter.