Hirotaka Nakamura

Reliable wide-area wavelength division multiplexing passive optical network accommodating gigabit ethernet and 10-Gb ethernet services

This paper proposes and demonstrates a reliable wide-area wavelength-division-multiplexing passive optical network (WDM-PON) with a wavelength-shifted protection scheme. This protection scheme utilizes the cyclic property of 2/spl times/N athermal arrayed-waveguide grating and two kinds of wavelength allocations, each of which is assigned for working and protection, respectively. Compared with conventional protection schemes, this scheme does not need a 3-dB optical coupler, thus leading to ensure the large loss budget that is suited for wide-area WDM-PONs. It also features a passive access node and does not have a protection function in the optical network unit (ONU). The feasibility of the proposed scheme is experimentally confirmed by the carrier-distributed WDM-PON with gigabit Ethernet interface (GbE-IF) and 10-GbE-IF, in which the ONU does not employ a light source, and all wavelengths for upstream signals are centralized and distributed from the central office.

New AC-Coupled Burst-Mode Optical Receiver Using Transient-Phenomena Cancellation Techniques for 10 Gbit/s-Class High-Speed TDM-PON Systems

An ac-coupled burst-mode receiver (B-Rx) for 10-Gbit/s class PON systems that uses a novel baseline-wander common-mode-rejection (BLW-CMR) technique and an inverted distortion technique is proposed and demonstrated. The realization of 10-Gbit/s class PON systems requires the development of a B-Rx with high sensitivity, a wide dynamic range, and a fast response for handling the burst-mode data. The BLW-CMR technique can cancel out the transient responses of capacitors at an ac-coupled interface, and the inverted distortion technique can reduce the duty-cycle distortion caused by the reference voltage wandering at long consecutive identical digits (CIDs) with a fast average detector. A B-Rx using these techniques can realize high receiver sensitivity, a wide dynamic range, and an instantaneous response with a high tolerance to CIDs. We achieved a settling time of less than 150 ns, a sensitivity of -29.8 dBm, and a dynamic range of 24.8 dB at a bit error rate of 10- 3 with a 231-1 pseudo random bit sequence for a burst-mode optical input at 10.3125 Gbit/s.

Flexible load balancing technique using dynamic wavelength bandwidth allocation (DWBA) toward 100Gbit/s-class-WDM/TDM-PON

This paper proposes a 100Gbit/s-class-WDM/TDM-PON system that uses wavelength tunability and DWBA to provide a flexible load balance and enlarged total bandwidth. An experiment of the downstream transmission clarifies the feasibility of the proposed system.

AC-Coupled Burst-Mode Transmitter Using Baseline-Wander Common-Mode-Rejection Technique for 10-Gbit/s-Class PON Systems

We propose and demonstrate an AC-coupled burst-mode transmitter with a differential interface for 10-Gbit/s-class passive optical network (PON) systems by using a novel baseline-wander common-mode-rejection (BLW-CMR) technique. This technique can cancel the transient responses of capacitors at the AC-coupled differential interface, and produce an optical burst-mode signal with a fast response. We confirmed the feasibility of this technique experimentally with the prototype we developed. The response time of the optical burst-mode signal was 500 ps, which is the fastest response time reported for a burst-mode transmitter. Good temperature dependences were also observed. Moreover, we conducted a burst-mode upstream experiment using a burst-mode avalanche photodiode (APD) receiver that we developed for 10 G-EPON systems. We obtained a large loss budget of 33 dB and a wide dynamic range of 25.5 dB at a bit error rate (BER) of 10-3.

First demonstration of fast automatic-gain-control (AGC) PDFA for amplifying burst-mode PON upstream signal

The effectiveness of installing fast AGC in a PDFA for amplifying burst mode PON upstream signals is reported for the first time. The technique has the potential to realize high-gain/high-power burst-mode PON repeaters.

Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers

A novel method for characterising the full spectrum of deuteron ions emitted by laser driven multi-species ion sources is discussed. The procedure is based on using differential filtering over the detector of a Thompson parabola ion spectrometer, which enables discrimination of deuterium ions from heavier ion species with the same charge-to-mass ratio (such as C(6+), O(8+), etc.). Commonly used Fuji Image plates were used as detectors in the spectrometer, whose absolute response to deuterium ions over a wide range of energies was calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium ion spectrum diagnosed in a recent experimental campaign is presented, which was produced from a thin deuterated plastic foil target irradiated by a high power laser.

Numerical Analysis of Dynamic SNR Management by Controlling DSP Calculation Precision for Energy-Efficient OFDM-PON

We propose a novel energy-saving technique using a variable precision digital signal processor for an orthogonal frequency division multiplexing (OFDM)-passive optical network. Our technique minimizes energy consumption while satisfying the bit error rate requirements by controlling the calculation precision of fast Fourier transform (FFT) and inverse FFT when generating an OFDM signal. We clarify the feasibility of our proposed technique numerically for QPSK and 16 quadratic-amplitude modulation signals. The simulation results indicate that calculation precision can be reduced according to the transmission distance.

Compact laser accelerators for X-ray phase-contrast imaging

Advances in X-ray imaging techniques have been driven by advances in novel X-ray sources. The latest fourth-generation X-ray sources can boast large photon fluxes at unprecedented brightness. However, the large size of these facilities means that these sources are not available for everyday applications. With advances in laser plasma acceleration, electron beams can now be generated at energies comparable to those used in light sources, but in university-sized laboratories. By making use of the strong transverse focusing of plasma accelerators, bright sources of betatron radiation have been produced. Here, we demonstrate phase-contrast imaging of a biological sample for the first time by radiation generated by GeV electron beams produced by a laser accelerator. The work was performed using a greater than 300 TW laser, which allowed the energy of the synchrotron source to be extended to the 10–100 keV range.

Selective deuterium ion acceleration using the Vulcan petawatt laser

We report on the successful demonstration of selective acceleration of deuterium ions by target-normal sheath acceleration (TNSA) with a high-energy petawatt laser. TNSA typically produces a multi-species ion beam that originates from the intrinsic hydrocarbon and water vapor contaminants on the target surface. Using the method first developed by Morrison et al. [Phys. Plasmas 19, 030707 (2012)], an ion beam with >99% deuterium ions and peak energy 14 MeV/nucleon is produced with a 200 J, 700 fs, >1020W/cm2 laser pulse by cryogenically freezing heavy water (D2O) vapor onto the rear surface of the target prior to the shot. Within the range of our detectors (0°–8.5°), we find laser-to-deuterium-ion energy conversion efficiency of 4.3% above 0.7 MeV/nucleon while a conservative estimate of the total beam gives a conversion efficiency of 9.4%.

Energy efficient IM-DD OFDM-PON using dynamic SNR management and adaptive modulation

This paper describes the demonstration of an energy efficient orthogonal frequency division multiplexing passive optical network using the dynamic signal to noise ratio (SNR) management and adaptive modulation. Controlling the calculation precision and modulation format minimizes the energy consumption of digital signal processor while satisfying the requirements of bit error ratio. We show that the calculation precision and modulation format can be optimized according to the optical received power, and realize a 58.7% effective energy efficiency per bit in an FPGA-based receiver experimentally.