300-Gb/s eye-diagram measurement by optical sampling usingfiber-based parametric amplification

In this letter, we report on up to 300-Gb/s real-time all-fiber-based optical eye-diagram measurements with 1.6-ps temporal resolution and 5-Hz refresh rate by all-optical sampling using parametric amplification in a short (50 m) highly nonlinear fiber. This represents, to the best of our knowledge, the highest bit-rate eye-diagram measurement so far, as well as the first demonstration of a fiber-based eye analyzer. The sensitivity and operational optical bandwidth is comparable to previously reported state-of-the-art nonlinear crystal-based sampling systems. We believe our results show that fiber-based optical sampling is indeed a potential candidate for characterization of future ultrahigh bit-rate optical communication systems     

High-performance optical-fiber-nonlinearity-based optical waveform monitoring

An all-optical waveform sampling system with simultaneous submilliwatt optical signal sensitivity (20-dB signal-to-noise ratio) and subpicosecond temporal resolution over more than 60-nm optical bandwidth is demonstrated in this paper. The optical sampling was implemented by four-wave mixing in a 10-m highly nonlinear fiber using a sampling pulse source with a sampling pulse peak power of only 16 W. The sampling performance was evaluated in terms of sensitivity, temporal resolution, and optical bandwidth with respect to fiber length, sampling pulse source wavelength offset from the zero-dispersion wavelength of the highly nonlinear fiber, sampling pulse peak power, and walk-off due to chromatic dispersion. This paper also presents a summary of the available methods to achieve polarization-independent optical sampling as well as a brief summary of the available sampling pulse sources viable for optical sampling.     

Fiber-based optical parametric amplifiers and their applications

An applications-oriented review of optical parametric amplifiers in fiber communications is presented. The emphasis is on parametric amplifiers in general and single pumped parametric amplifiers in particular. While a theoretical framework based on highly efficient four-photon mixing is provided, the focus is on the intriguing applications enabled by the parametric gain, such as all-optical signal sampling, time-demultiplexing, pulse generation, and wavelength conversion. As these amplifiers offer high gain and low noise at arbitrary wavelengths with proper fiber design and pump wavelength allocation, they are also candidate enablers to increase overall wavelength-division-multiplexing system capacities similar to the more well-known Raman amplifiers. Similarities and distinctions between Raman and parametric amplifiers are also addressed. Since the first fiber-based parametric amplifier experiments providing net continuous-wave gain in the for the optical fiber communication applications interesting 1.5-μm region were only conducted about two years ago, there is reason to believe that substantial progress may be made in the future, perhaps involving "holey fibers" to further enhance the nonlinearity and thus the gain. This together with the emergence of practical and inexpensive high-power pump lasers may in many cases prove fiber-based parametric amplifiers to be a desired implementation in optical communication systems     

Transparent wavelength conversion in fibre with 24 nm pump tuningrange

A transparent continuous wave-pumped highly nonlinear fibre wavelength converter (WC) with a conversion bandwidth of 61 nm and a pump wavelength tuning range of 24 nm, the largest ever reported for fibre-based WCs, is demonstrated. The conversion quality is confirmed by bit error rate measurements showing < 1.4 dB power penalty at 10 Gbit/s data transmission     

Broad-band continuous-wave-pumped fiber optical parametricamplifier with 49-dB gain and wavelength-conversion efficiency

A broad-band continuous-wave (CW) pumped fiber-based parametric amplifier with 39 dB of internal gain and wavelength conversion efficiency, corresponding to a black box gain/efficiency of 38 dB, is demonstrated. Bit-error-rate (BER) measurements indicate performance comparable to erbium-doped fiber amplifiers (EDFAs). These amplifiers may thus find new applications in future lightwave systems     

Measurement of ultralow Gordon-Haus timing jitter in dispersion-managed soliton systems

We measure, for the first time, the growth of the Gordon-Haus timing jitter in dispersion-managed soliton communication systems without inline soliton control. After 650-km transmission with a relatively high average dispersion of 0.87 ps/nm/km and a pulsewidth of 14 ps, compatible with 20 Gb/s, we measure a very low timing jitter of 45 fs. Hence, medium range dispersion-managed soliton transmission systems have, in general, a good margin toward Gordon-Haus timing jitter.     

Increase of the SBS threshold in a short highly nonlinear fiber byapplying a temperature distribution

We evaluate numerically and experimentally the stimulated Brillouin scattering (SBS) threshold increase for a short, highly nonlinear GeO₂-doped fiber by applying different temperature distributions along the fiber. The temperature coefficient for the Brillouin frequency downshift is measured to 1.2 MHz/°C. A threefold SBS threshold increase is obtained for a 100-m long highly nonlinear fiber with a 140°C temperature gradient. The proposed scheme is implemented in a wavelength converter based on fiber optical four-wave mixing (FWM). The SBS suppression scheme shows negligible influence on the FWM efficiency as well as the wavelength conversion bandwidth. The temperature coefficient for the zero dispersion wavelength is measured to 0.062 nm/°C     

Prescaled clock recovery based on small timing misalignment of datapulses

A simple and robust prescaled clock recovery technique is analyzed and demonstrated. An electrical clock is extracted from an ultra-high-speed time-division multiplexed (TDM) RZ signal using a “classic” approach to clock recovery with a detector and a bandpass filter (BPF). A subharmonic tone at the base rate frequency is generated by inducing a small misalignment between adjacent pulses in the transmitted data. The subharmonic tone is recovered as a clock signal at the receiver. Numerical calculations clarify the effect of filter bandwidth, word length, and strength of timing shift on the received timing jitter. Furthermore, it is found numerically that correlated TDM channels will decrease the jitter of the recovered clock considerably. A clock recovery circuit is implemented into an experimental 40 Gb/s and 80 Gb/s optical TDM (O-TDM) system without any observed penalty. Measurements of the timing jitter of the recovered prescaled clock have been performed to verify the numerical results. A 10 GHz clock signal with subpicosecond root-mean-square timing jitter is recovered from a 40-Gb/s O-TDM sequence without a phase-locked loop (PLL) configuration. By using a PLL-configuration, the timing jitter is reduced further by 50%. A discussion on the influence on transmission capacity is performed in general and for nonlinear optical communication systems in particular     

Wavelength tunable 40GHz pulse source based on fibre opticalparametric amplifier

A simple, wavelength tunable 40 GHz RZ source based on a fibre optical parametric amplifier is demonstrated. By using a 40 GHz sinusoidally intensity modulated pump, stable, nearly chirp free, high-power, 2-4 picosecond-wide pulses are obtained over 37 nm, extended into the L-band