Shu Namiki

Self-switching of optical pulses in dispersion-imbalanced nonlinear loop mirrors.

We report a novel nonlinear filter that transmits and shortens incident pulses while rejecting cw background as well as resonant continuum. A relative extinction of 22dB is reported for the cw background.

100 nm bandwidth flat gain Raman amplifiers pumped and gain-equalized by 12-wavelength-channel WDM high power laser diodes

We demonstrate 100 nm bandwidth Raman amplifiers using 12-wavelength-channel WDM pump laser diode unit. The gain flatness is less than /spl plusmn/0.5 dB, which is achieved through an asymmetric channel allocation of pump and without any gain equalization filters.

Noise of the stretched pulse fiber laser. I. Theory

A perturbation formalism is developed for the passively mode-locked stretched pulse fiber ring laser analogous to that of the fiber ring soliton laser. It is applied to determine the amplitude fluctuations, carrier frequency noise, and the pulse to pulse jitter due to the amplifier spontaneous emission noise.

Ultrahigh-Definition Video Transmission and Extremely Green Optical Networks for Future

The Internet traffic is essentially increasing because the contents are more associated with video, a higher definition video, rather than just text or picture. In fact, next-generation television (TV) standards are being explored toward the so-called 8-k definition, or ultrahigh-definition TV (UHDTV) that requires a bandwidth more than 70 Gb/s for real-time transmission. In the long run, chunks of such video data will eventually prevail over the network, and this trend would ensure a persistent traffic growth for the next decades to come. However, we will point out that the present IP-based technology cannot scale to the increasing traffic for the future mostly due to energy-consumption limits and will become a grave bottleneck for the sustainable growth of the traffic. We will then argue that the only promising solution for this would be the utilization of optical circuit switching, potentially having a few digits better energy efficiency than the present IP-router-based network. As specific implications, we are proposing the concept of the dynamic optical-path network (DOPN). We discuss how to scale the DOPN to the WAN, and show that an extremely green optical network for video-related services is possible at a clean-slate level. Then, we argue that DOPN will be first applied to LANs for broadcasting stations where a technology for scalable network interface cards are essential to accommodate the real-time UHDTV transmissions. Finally, we will briefly introduce our recent demonstration of UHDTV video transmissions using the optical time-division multiplexing based on integratable ultrafast optical devices only.

Cost-effective depolarized diode pump unit designed for C-band flat-gain Raman amplifiers to control EDFA gain profile

A cost-effective pumping unit with only two depolarized pump LDs for C-band flat-gain Raman amplifiers is proposed. The Raman gain in DCF is applied to simultaneously control the overall gain and gain flatness of an in-line EDFA.

Design considerations of all-optical A/D conversion: nonlinear fiber-optic Sagnac-loop interferometer-based optical quantizing and coding

The authors describe in detail the design considerations of our previously proposed novel optical quantizing and coding method for all-optical analog-to-digital (A/D) conversion using nonlinear optical switches based on the Sagnac interferometer. The multiperiod transfer function, which is the key to quantizing and coding, is achieved through a careful design of the Sagnac interferometer. In the experiments, the intensity of the pulse train input to our A/D converter is manually changed, and the corresponding digital signals are successfully mapped generated. Although the input-pulse trains are not the sampling of real analog signal, the principle of our proposed 3-bit A/D conversion at a 10 gigasample per second (Gsps) rate is demonstrated. The proposed optical quantizing and coding, combined with existing optical sampling techniques, will enable ultrafast photonic A/D conversion without electronics. The potential in the frequency regime of over a few hundred gigasamples per second was investigated by using an optical switch that utilizes the optical Kerr effect for fast operation. It was found out that the wavelength allocations and temporal widths of control and probe pulses have to be optimized with respect to the group-velocity dispersion of highly nonlinear fiber.

Wide-Band and -Range Tunable Dispersion Compensation Through Parametric Wavelength Conversion and Dispersive Optical Fibers

An intrinsically ultrafast, wide-band, and -range tunable dispersion compensation (TDC) is realized through parametric wavelength conversion in conjunction with fibers with large dispersion slope such as dispersion compensating fibers. The proposed schemes have unique potentials that they can operate with fast response in a truly colorless manner and are capable of producing two orders of magnitude larger bandwidth-dispersion product than conventional ones. After the discussions on the operating principle and design issues, a proof-of-concept experiment is performed to verify the static operations achieving a tunable dispersion range larger than plusmn280.5 ps2 for 2.47 ps optical pulses.

Energy consumption targets for network systems

Followed by related development activities in Japan, a comprehensive investigation on energy consumption in ITC industry is presented. Photonic network will have more important roles in mobile networks than in fixed networks.

Optical pulse compression based on stationary rescaled pulse propagation in a comblike profiled fiber

In this paper, optical pulse compression using a comblike profiled fiber (CPF) is theoretically and experimentally studied, in which highly nonlinear fibers and single-mode fibers are alternately concatenated. Stationary rescaled pulse (SRP), is the main focus, which is a recently discovered nonlinear stationary pulse in CPF. The fundamental characteristics of SRP are investigated, and SRP propagation is applied to the design of the CPF pulse compressor. Using the proposed design method, the specifications of the CPF can easily be controlled, such as the compression ratio per step of the CPF or the pedestal of the output pulse. Two experimental results of pulse compression using the CPF based on the proposed design method are shown: 1) pulse compression with a large compression ratio per step of the CPF and 2) low-pedestal and wideband wavelength-tunable compression. A parametric noise-amplification phenomenon occurring in a compression process for an optical pulse sequence is also numerically analyzed.

Observation of nearly quantum-limited timing jitter in an all-fiber ring laser

The Haus–Mecozzi theory of timing jitter and amplitude fluctuations of a self-starting additive-pulse mode-locked fiber ring laser operating in the negative group-velocity regime is reviewed. Experimental results confirm the theoretical predictions. The measured timing jitter has two physical origins. One is amplified spontaneous emission (quantum noise). The other is the amplitude fluctuation that is due to the pump source. The jitter is due mainly to the amplified spontaneous emission and is thus quantum limited.