Bill P.-P. Kuo

50-Gb/s Silicon Optical Modulator

Optical modulators formed in silicon are the keystone to many low cost optical applications. Increasing the data rate of the modulator benefits the efficiency of channel usage and decreases power consumption per bit of data. Silicon-based modulators which operate via carrier depletion have to the present been demonstrated at data rates up to 40 Gb/s; however, here we present for the first time optical modulation at 50 Gb/s with a 3.1-dB extinction ratio obtained from carrier depletion based phase shifter incorporated in a Mach-Zehnder interferometer. A corresponding optical insertion loss of approximately 7.4 dB is measured.

Generation of wideband frequency combs by continuous-wave seeding of multistage mixers with synthesized dispersion

We numerically and experimentally demonstrate efficient generation of an equalized optical comb with 150-nm bandwidth. The comb was generated by low-power, continuous-wave seeds, eliminating the need for pulsed laser sources. The new architecture relies on efficient creation of higher-order mixing tones in phase-matched nonlinear fiber stages separated by a linear compressor. Wideband generation was enabled by precise dispersion engineering of multiple-stage parametric mixers.

Wavelength Multicasting of 320-Gb/s Channel in Self-Seeded Parametric Amplifier

We report the first 320-Gb/s all-optical wavelength multicast experimental demonstration in two-pump parametric amplifier, assisted by pump-pump self seeding. A single 320-Gb/s channel was successfully multicast to eight wavelengths with minimal conversion efficiency of -1 dB and less than 5-dB gain ripple. Self seeding was achieved by efficient spectral management and optimization of multiple-pump phase. The Q -factor penalty induced by the self-seeding process was found to be less than 1 dB compared to the single-pump parametric wavelength conversion.

Wavelength Multicasting via Frequency Comb Generation in a Bandwidth-Enhanced Fiber Optical Parametric Mixer

We demonstrate a self-seeded multicasting device capable of delivering a large number of signal integrity preserving spectrally-distinct copies. The new multicasting device relies on efficient higher-order mixing in a two-pump parametric mixer. Precise dispersion engineering was deployed to generate a frequency-comb spanning over a 140-nm band, and resulted in the creation of more than 60 spectral copies of the signal with conversion efficiencies higher than -3 dB. The fidelity of the multicasting device with respect to signal intensity and phase was characterized experimentally. The spectral replication process was found to induce low penalty with both ON-OFF and differential phase-shift keying signals, thereby indicating compatibility with arbitrary amplitude/phase signaling formats.

Spectral linewidth preservation in parametric frequency combs seeded by dual pumps

We demonstrate new technique for generation of programmable-pitch, wideband frequency combs with low phase noise. The comb generation was achieved using cavity-less, multistage mixer driven by two tunable continuous-wave pump seeds. The approach relies on phase-correlated continuous-wave pumps in order to cancel spectral linewidth broadening inherent to parametric comb generation. Parametric combs with over 200-nm bandwidth were obtained and characterized with respect to phase noise scaling to demonstrate linewidth preservation over 100 generated tones.

Ultra-Wideband Pulse Generation Based on Cross-Gain Modulation in Fiber Optical Parametric Amplifier

A novel approach to generate ultra-wideband (UWB) monocycle or doublet pulse using cross-gain modulation in fiber optical parametric amplifier is demonstrated in a single experimental setup. The high-speed optical parametric process realizes the signal amplification, idler generation, and pump depletion simultaneously within femtosecond response time in the highly nonlinear fiber. After the combination of the three lightwaves with a suitable time delay between them, UWB pulse is obtained. A selective generation of monocycle or doublet pulse can be made by altering the optical attenuators without changing the wavelengths or the powers of the pump and the signal. In our experiment, high-quality UWB monocycle and doublet pulses with a fractional bandwidth of 115% and 126% were generated.

Spectrally Equalized Frequency Comb Generation in Multistage Parametric Mixer With Nonlinear Pulse Shaping

A novel approach to improve the flatness of wide-band parametric frequency combs is presented. The method relies on nonlinear pulse shaping prior to parametric mixing in a comb-generating device. The parametric comb is generated in a cavity-less multistage shock-wave mixer, using continuous-wave (CW) laser as comb seed. The pulse shaping is accomplished in a regenerative stage incorporating nonlinear optical/amplifying loop mirror (NOLM/NALM) and provides near-ideal seeds for spectrally equalized frequency comb generation in the output mixing stage. The new technique was implemented separately on two comb generators with a coarse (100 GHz) and dense (10 GHz) tone spacing. A 4 dB flatness over 100 nm is achieved with wide-pitched comb, while the fine-pitched device yielded 1500 tones and possessed sub-2 dB spectral flatness over 120 nm bandwidth.

Optical Demultiplexing of 320 Gb/s to 8

In this paper, we report the experimental demonstration of 320 Gb/s demultiplexing to eight simultaneous always-on 40 Gb/s tributaries with near-zero latency. The single-channel, single-polarization 320 Gb/s optical-time-division-multiplexed signal was processed by a copy-and-sample-all architecture. 1-to-8 wavelength multicasting over more than 10 THz of bandwidth was achieved in a self-seeded two-pump parametric amplifier, and was followed by a single gate, multicolored sampling with equalized response over more than 20 THz. The single gate operation allows for truly scalable real-time processing while avoiding the complexity of parallel pipelines processing. Error-free performance was measured over all extracted 40 Gb/s tributaries with less than 4 dB power penalty compared to conventional single tributary gating.

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Conventional highly-nonlinear fiber (HNLF) designs are optimized for high field-confinement but are also inherently susceptible to dispersion fluctuations. The design compromise prevents fiber-optical parametric mixers from possessing high power efficiency and extended operating bandwidth simultaneously. Using a new fiber waveguide design, we have fabricated and tested a new class of HNLF that possesses a significantly lower level of dispersion fluctuations while maintaining a high level of field-confinement comparable to that in conventional HNLFs. The fiber was used to demonstrate an all-fiber parametric oscillator operating in short-wavelength infrared (SWIR) band with a watt-level pump, for the first time.

40 Gb/s in Single Parametric Gate

Two novel bandwidth efficient pump-dithering Stimulated Brillouin Scattering (SBS) suppression techniques are introduced. The techniques employ a frequency-hopped chirp and an RF noise source to impart phase modulation on the pumps of a two pump Fiber Optical Parametric Amplifier (FOPA). The effectiveness of the introduced techniques is confirmed by measurements of the SBS threshold increase and the associated improvements relative to the current state of the art. Additionally, the effect on the idler signal integrity is presented as measured following amplification from a two pump FOPA employing both techniques. The measured 0.8 dB penalty with pumps dithered by an RF noise source, after accruing 160 ps/nm of dispersion with 38 dB conversion gain in a two-pump FOPA is the lowest reported to date.