Ryan P. Scott

Demonstration of free space coherent optical communication using integrated silicon photonic orbital angular momentum devices

We propose and demonstrate silicon photonic integrated circuits (PICs) for free-space spatial-division-multiplexing (SDM) optical transmission with multiplexed orbital angular momentum (OAM) states over a topological charge range of -2 to +2. The silicon PIC fabricated using a CMOS-compatible process exploits tunable-phase arrayed waveguides with vertical grating couplers to achieve space division multiplexing and demultiplexing. The experimental results utilizing two silicon PICs achieve SDM mux/demux bit-error-rate performance for 1‑b/s/Hz, 10-Gb/s binary phase shifted keying (BPSK) data and 2-b/s/Hz, 20-Gb/s quadrature phase shifted keying (QPSK) data for individual and two simultaneous OAM states.

High-dynamic-range laser amplitude and phase noise measurement techniques

We describe techniques for making sensitive and high-dynamic-range measurements of laser amplitude and envelope phase noise (timing jitter) in the frequency domain at the shot-noise limit. Examples of amplitude noise measurements on continuous-wave argon-ion and diode-pumped solid-state lasers used for pumping a femtosecond Ti:sapphire laser are presented. Amplitude and phase noise measurements for the Ti:sapphire laser are also presented, showing correlation between pump laser amplitude modulation (AM) spectra and the resulting AM and phase noise. Characteristics of the measurement system components are discussed, along with examples of the impact these have on achieving reliable high-dynamic-range measurement capability.

TEMPORAL MAGNIFICATION AND REVERSAL OF 100 GB/S OPTICAL DATA WITH AN UP-CONVERSION TIME MICROSCOPE

We have developed an up‐conversion time microscope capable of expanding ultrafast optical wave forms to a time scale accessible to ordinary sampling oscilloscopes. In this system, a 100 Gb/s optical word is magnified (slowed down) to a rate of 8.55 Gb/s with a time lens placed between two dispersive delay lines. The time lens is a nonlinear crystal which mixes the dispersed data with a linearly chirped pump pulse thus imparting a linear frequency sweep to the unconverted wave form. A second dispersive delay line completes the arrangement and forms the temporal analog of a single lens spatial imaging system resulting in a time reversed wave form with a magnification M=−11.7.

Spectral phase-encoded time-spreading (SPECTS) optical code-division multiple access for terabit optical access networks

This paper discusses design, simulation, and experimental investigations of optical-code-division multiple-access (O-CDMA) networking using a spectral phase-encoded time spreading (SPECTS) method. O-CDMA technologies can potentially provide flexible access of optical bandwidths in excess of 1Tb/s without relying on wavelength- or time-division-multiplexing modules, provided that they overcome the interference caused by other users broadcasting over the same channel, called multiuser interference (MUI). This paper pursues theoretical and experimental methods to mitigate the MUI. Analysis shows that nonuniform phase coding can increase the orthogonality of the code set, thereby reducing the impact of the MUI. The experiment conducted in a SPECTS O-CDMA testbed incorporating a highly nonlinear thresholder demonstrated error-free operation for four users at 1.25-Gb/s/user and for two users at 10-Gb/s/user.

32 Phase X 32 amplitude optical arbitrary waveform generation.

We describe the precise shaping and mode-resolved amplitude and phase characterization of optical arbitrary waveforms by using a 20 GHz optical frequency comb and integrated 64 x 20 GHz channel arrayed waveguide grating pair. Complex waveforms with large variations in phase and amplitude between adjacent modes were generated and characterized.

Tb/s Coherent Optical OFDM Systems Enabled by Optical Frequency Combs

This paper discusses the realization of terabit per second high speed and high spectral-efficiency optical transmissions using much lower speed electronics and optoelectronics through parallel processing of coherent optical frequency combs at both the transmitter and receiver. The coherent and parallel processing enables electrical-to-optical and optical-to-electrical (E/O and O/E) conversion of wide-bandwidth optical signals which would otherwise exceeds the capability of conventional optoelectronics. In the first experiment, an optical frequency comb (OFC) generator provides 32 comb lines with less than 5-dB power variation. Subsequently, 1.008-Tb/s modulation capability is realized on 32 × 106 OFDM subcarriers with 16-QAM modulation in a 318-GHz seamless optical bandwidth. It demonstrates an effective way to generate an optical OFDM signal with tens of times wider optical bandwidth than that of analog-to-digital converters and digital-to-analog converters (ADC/DAC). The second experiment demonstrates simultaneous detection of multiple OFDM bands from a 32-band coherent optical OFDM signal using another optical frequency comb, a silica planar lightwave circuit (PLC) that implemented the major optical devices, and two pairs of balanced photodiodes. The experimental results indicate prospects for an optically integrated coherent optical OFDM system on a chip-scale platform.

Demonstration of an error-free 4 /spl times/ 10 Gb/s multiuser SPECTS O-CDMA network testbed

We demonstrate an error-free four-user 10-Gb/s/user optical code-division multiple-access network testbed employing the spectral phase encoded time spreading technique and nonlinear thresholding. The experiments successfully overcome multiuser interference, resulting in error-free operation.

Bandwidth scalable, coherent transmitter based on the parallel synthesis of multiple spectral slices using optical arbitrary waveform generation

We demonstrate an optical transmitter based on dynamic optical arbitrary waveform generation (OAWG) which is capable of creating high-bandwidth (THz) data waveforms in any modulation format using the parallel synthesis of multiple coherent spectral slices. As an initial demonstration, the transmitter uses only 5.5 GHz of electrical bandwidth and two 10-GHz-wide spectral slices to create 100-ns duration, 20-GHz optical waveforms in various modulation formats including differential phase-shift keying (DPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK) with only changes in software. The experimentally generated waveforms showed clear eye openings and separated constellation points when measured using a real-time digital coherent receiver. Bit-error-rate (BER) performance analysis resulted in a BER < 9.8 × 10(-6) for DPSK and QPSK waveforms. Additionally, we experimentally demonstrate three-slice, 4-ns long waveforms that highlight the bandwidth scalable nature of the optical transmitter. The various generated waveforms show that the key transmitter properties (i.e., packet length, modulation format, data rate, and modulation filter shape) are software definable, and that the optical transmitter is capable of acting as a flexible bandwidth transmitter.

Free-space coherent optical communication with orbital angular, momentum multiplexing/demultiplexing using a hybrid 3D photonic integrated circuit

We demonstrate free-space space-division-multiplexing (SDM) with 15 orbital angular momentum (OAM) states using a three-dimensional (3D) photonic integrated circuit (PIC). The hybrid device consists of a silica planar lightwave circuit (PLC) coupled to a 3D waveguide circuit to multiplex/demultiplex OAM states. The low excess loss hybrid device is used in individual and two simultaneous OAM states multiplexing and demultiplexing link experiments with a 20 Gb/s, 1.67 b/s/Hz quadrature phase shift keyed (QPSK) signal, which shows error-free performance for 379,960 tested bits for all OAM states.

An eight-user time-slotted SPECTS O-CDMA testbed: demonstration and simulations

This paper demonstrates an eight-user 9 Gb/s/user time-slotted spectral phase-encoded time-spreading (SPECTS) optical code division multiple access (O-CDMA) testbed. Experimentally measured performance is compared to numerical simulations. The testbed employs a novel compact fiber-pigtailed bulk-optics setup that utilizes a single two-dimensional (2-D) phase modulator for encoding multiple channels, each with a unique 64-chip Walsh code. The time-gated receiver is composed of a nonlinear optical loop mirror (NOLM) and a nonlinear thresholder each utilizing a highly nonlinear fiber (HNLF) as the nonlinear element. The testbed operates error free with up to six users and at a bit error rate BER<10/sup -9/ for eight simultaneous users. Careful modeling of each component in the testbed allows a close match between simulated and experimentally measured testbed performance.