Channel cloning by multi-mode phase-sensitive parametric mixer.

We investigate high fidelity channel replication approaching the idealized notion of channel cloning with negligible excess noise and distortion. Previously proposed cloning architectures require that the channel carriers to be externally seeded, limiting their ultimate usefulness, whereas the self-seeded approach limits the channel number and signal-to-noise ratio. Specifically, when a single channel is replicated, the noise figure (NF) remains above the well-known 3-dB limit, and multi-channel replication by a dual-pump driven parametric mixer faces a theoretical NF limit of 6-dB. On the other hand, large-channel-count cloning is of particular importance as it allows for rate scaling in generalized signal processing. Recognizing the limits of conventional architectures that rest on homogeneous parametric mixers, we here propose multi-stage, dispersion-managed parametric mixers in multi-mode phase-sensitive architecture to clone the input signal to a substantial number of channels. In particular, when the new mixer is operated in four-mode phase-sensitive architecture, a 17-copy-count channel cloning with maximum NF less than 6-dB and a record-low NF of 2-dB was experimentally implemented and demonstrated in this paper.

All optical wavelength multicaster and regenerator based on four-mode phase-sensitive parametric mixer.

Four-mode phase-sensitive (4MPS) process has been employed in a parametric mixer based wavelength multicaster, enhancing the multicasting conversion efficiency and signal-to-noise ratio. In addition, the 4MPS parametric multicaster is an outstanding candidate for all-optical regeneration, owing to its inherent capabilities to clamp amplitude fluctuations by the saturated parametric effect and to squeeze phase distortions by the phase sensitive process. The investigation in this paper focuses on the 4MPS multicaster operated in the saturation gain regime, including theoretical simulations and experimental demonstrations on amplitude and phase noise regeneration over 20 multicasting signal copies.

Resonant reflection spectroscopy of biomolecular arrays in muscle.

Sarcomeres, the functional units of contraction in striated muscle, are composed of an array of interdigitating protein filaments. Direct interaction between overlapping filaments generates muscular force, which produces animal movement. When filament length is known, sarcomere length successfully predicts potential force, even in whole muscles that contain billions of sarcomere units. Inability to perform in vivo sarcomere measurements with submicrometer resolution is a long-standing challenge in the muscle physiology field and has hampered studies of normal muscle function, adaptation, injury, aging, and disease, particularly in humans. Here, we develop theory and demonstrate the feasibility of to our knowledge a new technique that measures sarcomere length with submicrometer resolution. In this believed novel approach, we examine sarcomere structure by measuring the multiple resonant reflections that are uniquely defined by Fourier decomposition of the sarcomere protein spatial framework. Using a new supercontinuum spectroscopic system, we show close agreement between sarcomere lengths measured by resonant reflection spectroscopy and laser diffraction in an ensemble of 10 distinct muscles.

All-optical switching in a highly efficient parametric fiber mixer: design study.

Ultrafast all-optical switching in a highly nonlinear fiber with a longitudinally varied zero-dispersion wavelength was investigated theoretically and experimentally. We describe fiber-matched methodology for construction of a fast, low energy photon switch. The design relies on static and dynamic models and allows performance target selection, under constraints of physical fiber characteristic. The new design methodology was used to construct one-pump switch in the highly efficient parametric mixer. We demonstrate that such a parametric gate can operate at 100 GHz rate, with 2 aJ control energy, while achieving better than 50% extinction ratio. Theoretical analysis and experimental measurements indicate that accurate mapping of the fiber local dispersion is critical in optimizing the bandwidth and control energy of the switch. Switching performance limits are discussed and means for impairment mitigation are described.

Low-noise parametric frequency comb for continuous C-plus-L-band 16-QAM channels generation.

A low phase noise frequency comb generated from a continuous-wave seed is experimentally demonstrated across continuous C- and L-bands. Parametrically generated carriers with optical signal-to-noise ratio in excess of 45 dB were used to generate 16-ary quadrature amplitude modulated signals. We characterize 20 GBaud channels' performance that was varied by only 1.7 dB across the combined C/L band.

Digital multi-channel stabilization of four-mode phase-sensitive parametric multicasting.

Stable four-mode phase-sensitive (4MPS) process was investigated as a means to enhance two-pump driven parametric multicasting conversion efficiency (CE) and signal to noise ratio (SNR). Instability of multi-beam, phase sensitive (PS) device that inherently behaves as an interferometer, with output subject to ambient induced fluctuations, was addressed theoretically and experimentally. A new stabilization technique that controls phases of three input waves of the 4MPS multicaster and maximizes CE was developed and described. Stabilization relies on digital phase-locked loop (DPLL) specifically was developed to control pump phases to guarantee stable 4MPS operation that is independent of environmental fluctuations. The technique also controls a single (signal) input phase to optimize the PS-induced improvement of the CE and SNR. The new, continuous-operation DPLL has allowed for fully stabilized PS parametric broadband multicasting, demonstrating CE improvement over 20 signal copies in excess of 10 dB.

Noise performance of phase-insensitive multicasting in multi-stage parametric mixers.

Noise properties of large-count spectral multicasting in a phase-insensitive parametric mixer were investigated. Scalable multicasting was achieved using two-tone continuous-wave seeded mixers capable of generating more than 20 frequency non-degenerate copies. The mixer was constructed using a multistage architecture to simultaneously manage high Figure-of-Merit frequency generation and suppress noise generation. The performance was characterized by measuring the conversion efficiency and noise figure of all signal copies. Minimum noise figure of 8.09dB was measured. Experimental findings confirm that noise of the multicasted signal does not grow linearly with copy count and that it can be suppressed below this limit.

Noise performance of phase-insensitive frequency multicasting in parametric mixer with finite dispersion.

Noise performance of dual-pump, multi-sideband parametric mixer operated in phase-insensitive mode is investigated theoretically and experimentally. It is shown that, in case when a large number of multicasting idlers are generated, the noise performance is strictly dictated by the dispersion characteristics of the mixer. We find that the sideband noise performance is significantly degraded in anomalous dispersion region permitting nonlinear noise amplification. In contrast, in normal dispersion region, the noise performance converges to the level of four-sideband parametric process, rather than deteriorates with increased sideband creation. Low noise generation mandates precise dispersion-induced phase mismatch among pump and sideband waves in order to control the noise coupling. We measure the noise performance improvement for a many-sideband, multi-stage mixer by incorporating new design technique.

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.

Full characterization of self-phase-modulation based low-noise, cavity-less pulse source for photonic-assisted analog-to-digital conversion.

A high quality cavity-less pulse source, realized as a combination of linear pulse compression and self-phase-modulation (SPM) based regeneration is demonstrated and strictly characterized for the first time. The regenerated pulses, with 3.6 GHz repetition rate, are optimized through rigorous relative intensity-noise (RIN) measurement. Temporal intensity and chirp characterizations demonstrate that the pulses exhibit characteristic of low RIN, and are chirp- and pedestal-free. The cavity-less pulse source is further tested in a photonic-assisted analog-to-digital (ADC) configuration as the sampling source. A record result of more than 8 effective quantization bits at 202 MHz is demonstrated.

Pump noise cancellation in parametric wavelength converters.

A novel technique for pump noise effect mitigation in parametric wavelength converters is introduced. The method relies on digital signal processing and effectively takes advantage of the correlation property between the pump and idler, imposed by the parametric interaction. A 4 dB improvement in receiver performance is demonstrated experimentally for the conventional 10 Gbps OOK signal converted over 20 nm.

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.

Broadband parametric multicasting via four-mode phase-sensitive interaction.

Optical frequency multicasting with significantly enhanced signal-to-noise-ratio (SNR) is demonstrated over wide wavelength range. High-fidelity multicasting relies on a four-mode phase-sensitive (PS) parametric process. Four-mode seeding was used to drive dual-pump, multistage mixer and achieve high-efficiency frequency comb generation and signal replication assisted by field interference. New PS mixer was measured to possess near 12-dB of spectrally uniform optical SNR advantage over conventional, phase-insensitive (PI) parametric multicaster. In signal attenuation regime, PS operation was measured with better than 10dB over the entire mixer band, indicating highly controllable PS interference. The role of the new PS mixer in near-noiseless signal replication is elaborated.

Photonic preprocessor for analog-to-digital-converter using a cavity-less pulse source.

A photonic preprocessor for analog to digital conversion is demonstrated and characterized using a cavity-less optical pulse source. The pulse source generates high fidelity pulses at 2 GHz repetition rate with temporal width of 3 ps. Chirped pulses are formed by cascaded amplitude and phase modulators, and subsequently compressed in dispersion compensating fiber. Sampling operation is performed with a dual-output Mach-Zehnder modulator, where the complimentary output enables a reduction of noise by 3 dB. Phase noise characterization shows that the phase noise of the generated pulses is fully dictated by the RF source. The high quality of the pulse source used in a sampling preprocessor experiment was verified by measuring 8 effective number of bits at 10 GHz and 7.0 effective number of bits at 40 GHz.

1.56-micros continuously tunable parametric delay line for a 40-Gb/s signal.

Experimental demonstration of an all-fiber, all-optical continuously tunable delay line is reported. The 1.56-micros delay with a record 62,400 time-delay bit-rate product was characterized for a 40-Gbps data channel. The result was enabled by parametric dispersion compensation with cascaded triple-conversion in highly-nonlinear fiber capable of continuous tuning over 39.5 nm.

2-Dimensional beamsteering using dispersive deflectors and wavelength tuning.

We introduce a 2D beamscanner which is controlled by wavelength tuning. Two passive dispersive devices are aligned orthogonally to deflect the optical beam in two dimensions. We provide a proof of principle demonstration by combining an arrayed waveguide grating with a free space optical grating and using various input sources to characterize the beamscanner. This achieved a discrete 10.3 degrees by 11 degrees output field of view with attainable angles existing on an 8 by 6 grid of directions. The entire range was reached by scanning over a 40 nm wavelength range. We also analyze an improved system combining a virtually imaged phased array with a diffraction grating. This device is much more compact and produces a continuous output scan in one direction while being discrete in the other.