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A photonic frequency up-conversion scheme based on the nonlinear polarization rotation (NPR) arising in a semiconductor optical amplifier for wavelength-division-multiplexing (WDM) baseband signals is proposed and experimentally demonstrated. Error-free simultaneous up-conversion of 4 times 2.5 Gb/s WDM baseband channels with a 20-GHz local oscillator signal is experimentally demonstrated in the whole C-band. Compared with the cross-gain-modulation-based scheme, the proposed scheme is found to be almost independent of the wavelength separation between the probe and pump signals. Both the radio-frequency spectrum and the bit-error-ratio performance after electrical down-conversion have shown low distortion induced by the optical NPR-based up-conversion.

We demonstrate a photonic monocycle pulse frequency up-conversion scheme for ultrawideband (UWB)-over-fiber applications using nonlinear polarization rotation arising in a semiconductor optical amplifier. For the first time, we have successfully realized the photonic up-conversion of UWB monocycle pulses with an optical local oscillator signal at 24 GHz in the whole -band. The up-converted UWB monocycle pulse at 24 GHz exhibits a power spectrum density fitting the UWB emission mask. After electrical down-conversion, the UWB monocycle pulse has shown low distortion induced by the optical mixing process.

We propose a novel optical carrier-reuse scheme for the wavelength-division-multiplexed passive optical network. The scheme is based on a single delay interferometer (DI) at the remote node and reflective semiconductor optical amplifiers (RSOAs) at optical network units as the colorless devices for upstream transmission. The downstream subcarrier signals are optically separated by the DI for baseband detection of the downstream data and the separated optical carriers are used for seeding the RSOAs. Eight-channel upstream and downstream transmission is demonstrated at 1.25 Gb/s using the proposed scheme. The impact of optical carrier-to-subcarrier ratio of downlink signal and seeding light power on performance is also investigated

All-optical clock recovery (CR) from 10-Gb/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signal is demonstrated experimentally by introducing the chromatic-dispersion-induced clock tone into a free-running semiconductor optical amplifier (SOA)-based fiber ring laser for achieving mode-locking. Since no special component is required for NRZ-DPSK demodulation, our proposed method is very promising because of its simple configuration and better stability. The good performance of our proposed configuration is fulfilled with a 20-km standard single-mode fiber to regenerate clock tone of the NRZ-DPSK signal. The recovered clock signal with the extinction ratio of 17 dB and the root-mean-square timing jitter of 718 fs is achieved under 231-1 pseudorandom binary sequence NRZ-DPSK signals measurement

Conventional on-off keyed signals, such as return-to-zero (RZ) and nonreturn-to-zero (NRZ) signals are susceptible to cross-gain modulation (XGM) in semiconductor optical amplifiers (SOAs) due to pattern effect. In this letter, XGM effect of Manchester-duobinary, RZ differential phase-shift keying (RZ-DPSK), NRZ-DPSK, RZ, and NRZ signals in SOAs were compared. The experimental results confirmed the reduction of crosstalk penalty in SOAs by using Manchester-duobinary signals

We experimentally study the impact of filter bandwidth of a spectrum-sliced amplified spontaneous emission (ASE) source on the injection-locking of a Fabry-Perot laser diode (FPLD) for passive optical network application. Optimal bandwidth of a spectrum-sliced ASE source was found in terms of receiver sensitivity after transmission. We also investigate the impact of intensity noise (IN) of the spectrum-sliced ASE source and its suppression for a wavelength-locked FPLD using a semiconductor optical amplifier. Experiment results show that the output performance of a wavelength-locked FPLD is improved by IN suppression

A Manchester-duobinary coding scheme is proposed to compact the optical spectrum compared with that using pure Manchester coding and thus demonstrate much larger tolerance against fiber dispersion. With this modulation format, the dispersion tolerance can be extended to nearly three times of that using pure Manchester coding. Dispersion tolerance of Manchester-duobinary is from -800 to +920 ps/nm at 2-dB power penalty

We demonstrate the use of an injection-locked Fabry-Peacuterot laser diode with electronic feedback for base-rate clock recovery in Ntimes10 Gb/s optical time-division-multiplexing (OTDM) systems. Injection-locking enhances the resonance frequency of the laser and the electrical feedback achieves strong resonance at the base-rate frequency of the injected data streams, enabling ultrastable electrical clock signal generation at the base rate of 10 GHz. Experimental demonstrations for clock recovery at 10 GHz from 40-Gb/s OTDM data streams and 4-1 demultiplexing of the data using the extracted clock after fiber transmission is presented. The timing jitter measured in the recovered electrical clock is less than 0.25 ps

We investigate the impairment induced by stimulated Brillouin scattering (SBS) effect and noise characteristics of wavelength-division-multiplexing fiber-radio network assisted by distributed Raman amplifier (DRA) or erbium-doped fiber amplifier. Experimental results indicate that forward-pumping DRA can increase the link optical output power limited by SBS effect in downstream transmission and backward-pumping DRA can improve signal-to-noise ratio in upstream transmission, which is verified by binary phase-shift keying transmission experiments. Moreover, our experimental results show that DRA does not introduce additional impairment from interchannel crosstalk due to cross-phase modulation and degradation in spur-free dynamic range

We investigate the effects of polarization-mode dispersion (PMD) and chirp on radio-frequency tone-based chromatic dispersion (CD) monitoring method, and show that the PMD and chirp induce significant CD monitoring errors. We propose a CD monitoring technique to suppress these effects. Experiment results show that the CD monitoring errors induced by PMD and chirp fluctuation are greatly suppressed.

To avoid significant stimulated Brillouin scattering (SBS) generation in a bidirectional Raman-pumped long single-span transmission system, the SBS threshold is studied in both return-to-zero on-off -keying (RZ-OOK) and RZ differential phase-shift keying (DPSK) systems. It shows that SBS threshold in an RZ-DPSK system is more than 10 dB higher than that in an RZ-OOK system, and SBS reflection is dominated by copumping, while counterpumping has minor effect. Error-free eight-channel single-span transmission is demonstrated over 310-km standard single-mode fiber using RZ-DPSK format and bidirectional Raman pumping, without applying forward-error correction and remote-pumping techniques.

This letter presents a novel scheme for polarization-insensitive optical clock recovery by preconditioning the data signal at the transmitter side. The polarization-insensitivity is realized by making the polarizations of two channels orthogonal in the second stage of optical time-domain multiplexing. A 38-GHz optical clock was recovered from the incoming data stream using a passively mode-locked multisection laser diode. The results show that the performance of the recovered 38-GHz clock is extremely insensitive to the polarization state of the incoming data.

We propose and demonstrate a simple technique to control rapid erbium-doped fiber amplifier (EDFA) transients in optical burst switched networks. We demonstrate a 6-dB transient reduction in a 10-Gb/s 80-km-long wavelength-division-multiplexing system with three EDFAs. We show through simulation that the technique can be used at the first EDFA in links of as many as ten EDFAs to control transients to within 2 dB.

This letter presents a novel configuration for return-to-zero (RZ) differential phase-shift keyed (DPSK), carrier-suppressed (CS) RZ DPSK, and chirped nonreturn-to-zero (CNRZ) signal generation, which only requires a single-stage dual-electrode Mach-Zehnder modulator (DE-MZM). RZ-DPSK, CSRZ-DPSK, or CNRZ signals can be generated via the same configuration by changing the DE-MZM operating conditions. Analytical derivation and simulation on signal generation and wavelength-division-multiplexed transmission was also carried out to justify the equivalence of the proposed scheme and conventional methods. The proposed scheme is expected to be more cost-effective due to the reduction in required modulator number.

In this letter, we propose a novel transmitter configuration for generating electrically band-limited (EB) carrier-suppressed return-to-zero (CSRZ) differential phase-shift-keyed (DPSK) signals, which requires only a single-stage Mach-Zehnder modulator in conjunction with an electrical band-limiting low-pass filter and electrical mixer. The proposed scheme is cost-effective due to the simple configuration. In addition, when applied to dense wavelength-division-multiplexing systems with high spectral efficiency, the EB-CSRZ-DPSK signal exhibits reduced linear crosstalk, increased dispersion tolerance, and no additional nonlinearity penalty in comparison to the conventional CSRZ-DPSK signal.

We present a new scheme for realizing optical clock recovery by injection locking a long cavity Fabry-Pe/spl acute/rot laser diode. A 32.48-GHz optical clock with low level of timing jitter (0.38 ps) and high extinction ratio (23 dB) was recovered from a 32.48-Gb/s return-to-zero input optical data stream. The impact of the characteristics of the input signal such as the injected optical power and tunability of data rate on the measured radio-frequency power, timing jitter, and extinction ratio of the recovered clock signal has also been investigated.

Generation of multichannel optical pulse trains by spectral slicing of two adjacent optical modes from a single subharmonically synchronous mode-locked laser diode is demonstrated in this letter. The obtained pulse source exhibits high extinction ratio (> 15 dB), low amplitude modulation (

This letter demonstrates a novel technique for the generation of a pulsed multichannel source from a multiple mode laser diode (LD). The pulsed multiple channel source with 6.5 GHz repetition rate was generated from a subharmonically hybrid mode-locked monolithic laser with 32.5 GHz mode spacing. The obtained pulse source exhibits high extinction ratio (>10 dB) and low level of root-mean-square (RMS) phase noise (

We present a novel configuration for carrier-suppressed return-to-zero (CSRZ) signal generation, which only requires a single-stage Mach-Zehnder modulator in conjunction with an electrical mixer. An electrical band-limiting filter is also introduced to further reduce the spectral width of the generated CSRZ signal. The proposed scheme is potentially cost-effective, and simulation results show that the electrically band-limited CSRZ signal exhibits larger dispersion tolerance than a conventional CSRZ signal without any degradation in its nonlinearity tolerance.

All-optical clock recovery at line rate (34 GHz) was demonstrated by narrow-band resonant modulation of a single-mode monolithic laser diode. The dependence of timing jitter of the recovered clock on frequency detuning and injected optical signal power has been investigated. This scheme does not require an intracavity saturable absorber and the recovered clock signal exhibits a large locking range.

A detailed comparison of the characteristics of 40-GHz pulses from a subharmonic mode-locked monolithic laser diode with and without a saturable absorber (SA) is demonstrated in terms of timing jitter, frequency detuning, amplitude modulation, and extinction ratio. The experimental results show that saturable absorption in the laser cavity improves the extinction ratio and suppresses amplitude modulation and timing jitter, while no SA section in the laser cavity is cost-effective and offers subharmonically mode-locked pulses a larger frequency detuning range.

The broad-band amplitude noise of 40-GHz pulses from a subharmonically synchronous mode-locked (SSML) semiconductor laser is investigated. Experiments show that the amplitude noise of pulses generated from a SSML laser depends on the amplitude noise and pulsewidth of injected pulses, frequency detuning and subharmonic numbers.

A new technique for generating millimeter-wave (mm-wave) signals from a semiconductor laser without an intracavity saturable absorber, is presented, The method multiplies the signal frequency by using optical injection of short optical pulses at a subharmonic of the cavity round-trip frequency to drive the laser oscillating at its resonant frequency. A 34.64 GHz signal is generated using a multisection semiconductor laser operated under continuous wave conditions, by injecting optical pulses at a repetition rate equal to the fourth subharmonic (8.66 GHz). The generated millimeter-wave signal exhibits a large subharmonic suppression ratio (>17 dB), large frequency detuning range (>300 MHz), low levels of phase-noise (-77.5 dBc/Hz), and large locking range (>400 MHz).

A Gaussian pulse with frequency chirping is transmitted in a dispersion management (DM) soliton system. The existence of an initial chirping makes the pulsewidth and amplitude fluctuate over distance around their initial values, and increases the energy enhancement factor. The quasi-transform-limited pulse generated with spectral windowing is also propagated in the DM soliton system. With proper energy enhancement, the quasi-transform-limited pulse can propagate very stably, and the performance is better than that in a uniform low dispersion soliton system, which suggests that a DM system has more chirping and waveform tolerance in soliton sources than a uniform fiber system.

The effects of carrier phase noise on the performance of long-distance soliton transmission system are analyzed. The arrival time jitter due to carrier linewidth is derived with initial value perturbation method, optical phase conjugation is used to suppress timing jitter, and a optimum design theory is given for long-distance soliton transmission system with optical source noise. Carrier phase noise increases the total timing jitter, changes the optimum position of conjugator, the optimum dispersion value and choosing range of dispersion in the transmission link. But an optimum dispersion range can still be found for 10 Gb/s, 10000 km soliton system even with optical source noise.