Tomotaka Nagashima

Resolution upgrade toward 6-bit optical quantization using power-to-wavelength conversion for photonic analog-to-digital conversion

We demonstrate a resolution upgrade toward 6 bit optical quantization using a power-to-wavelength conversion without an increment of system parallelism. Expansion of a full-scale input range is employed in conjunction with reduction of a quantization step size with keeping a sampling-rate transparency characteristic over several 100 sGS/s. The effective number of bits is estimated to 5.74 bit, and the integral nonlinearity error and differential nonlinearity error are estimated to less than 1 least significant bit.

Below 100-fs Timing Jitter Seamless Operations in 10-GSample/s 3-bit Photonic Analog-to-Digital Conversion

We experimentally realize seamless operations with below 100-fs timing jitter in a 10-GSample/s 3-bit photonic analog-to-digital converter (ADC) with an input 2.5-GHz sinusoidal electrical signal. To address the energy efficiency, it is necessary to explore some serial approaches to get most operations in a photonic ADC done before serial-to-parallel conversion to save the number of devices. To press forward with the work on subsequent operations after optical sampling in a photonic ADC, we have investigated optical quantization and coding and demonstrated their performances. The experimental results successfully demonstrated seamless operations in a photonic ADC, i.e., sampling, quantization, and coding, while keeping its parallel-configuration-free characteristics and low timing jitter below 100 fs. This demonstration could address the energy efficiency by reduction of the number of devices, including electrical ADCs for subsequent operations after optical sampling in existing high-performance photonic ADCs.

Flexible power-efficient Nyquist-OTDM transmitter, using a WSS and time-lens effect

Power-efficient, flexible, Nyquist 4.88-ps sinc-pulses generation and OTDM multiplexing is demonstrated, using fractional Fourier transform subcarriers and time-lens effect. OTDM users are generated and multiplexed by a WSS, without rectangular spectral shaping.

Fractional OFDM based transmitter and receiver for time/frequency multiplexing in gridless, elastic networks

We demonstrate for the first time optical fractional OFDM system, based on intermediate grids between time and frequency axes. Using reconfigurable wavelength selective switches, we demonstrated open eye diagrams, and performance below the FEC-limit.

Power-saving approach toward 7-bit optical quantization for photonic analog-to-digital conversion

We experimentally investigate the realization of low power consumption optical quantization with 7-bit resolution. We confirm the resolution improvement without increment of the signal power by incorporating the spectral compression technique using a phase modulator.

PAPR management of all-optical OFDM signal using fractional fourier transform for fibre nonlinearity mitigation

We propose a novel PAPR management technique using fractional Fourier transform subcarriers and time-lens effect. By deforming a high PAPR OFDM signal into a low PAPR Nyquist pulse train in fibre links, signal distortions by a fibre nonlinearity are mitigated.

Advanced Optical Pulse Signal Profiling using Distributable “Optical Pulse Ruler”

We propose and demonstrate advanced optical pulse signal profiling using a high-nonlinear optical fiber, which works as a distributable “optical pulse ruler”. Additionally, we assess its profiling performance by comparison with conventional instruments.

40 GSample/s All-Optical Analog to Digital Conversion With Resolution Degradation Prevention

In this letter, we report the experimental demonstration of a 40 GSample/s all-optical analog to digital converter (ADC). The proposed all-optical ADC consists of optical quantization and coding processes based on intensity-to-wavelength conversion by soliton self-frequency shift with an optical sampling process using an ultrastable optical pulse train. A 5-GHz sinusoidal analog input signal was successfully converted to a digitized output signal in real time with no degradation of resolution. (High sampling rate operation may lead to resolution degradation due to the reduction of pulse peak power and the narrowing of the interval between adjacent pulses.) To evaluate system performance, we estimated the effective number of bits from the experimental results as 3.79 b.

OFDM to OTDM conversion by fractional Fourier transform

A pioneering energy-efficient all-optical system to transform an OFDM signal into an OTDM data flow is proposed and experimentally demonstrated for the first time, based on an innovative fully passive AWG device that implements the fractional Fourier transform.

OFDM to OTDM Conversion by Optical Fractional Fourier Transform

A new AWG device has been designed and fabricated to implement the fractional Fourier transform and allow all-optical spectral and time signal manipulation. 12-channel OFDM to OTDM conversion has been experimentally demonstrated.