Mitsuhiro Teshima

Performance of multiwavelength simultaneous monitoring circuit employing arrayed-waveguide grating

This paper proposes a novel multiwavelength simultaneous monitoring (MSM) circuit that uses the wavelength crossover properties of an arrayed-waveguide grating (AWG). The MSM circuit consists of an AWG, a stabilized semiconductor laser as a reference light, and logarithmic amplifiers. The AWG chip is a simple planar-lightwave-circuit chip. It functions as multiple optical filters, and make it possible to monitor multiple wavelengths simultaneously. The MSM circuit, locked to the reference wavelength produced by a semiconductor laser stabilized to the 1547.49 mn /sup 13/C/sub 2/H/sub 2/ absorption line, achieved 10 MHz resolution and 30 MHz stability for 24 h in the stable polarization state. Measurement accuracy of better than 1.1 GHz can be realized even if the state of polarization of the input light fluctuates at random. Multiwavelength simultaneous monitoring is successfully demonstrated using tunable lasers.

Super-dense WDM transmission of spectrum-sliced incoherent light for wide-area access network

This paper presents a detailed study on superdense wavelength-division multiplexing (WDM) transmission of spectrum-sliced incoherent light used for a wide-area access network. The transmission performance possible with this approach is evaluated numerically with regard to the following items: the transmission limit due to the chromatic dispersion, optimized signal-to-noise ratio design for the optical spectral width taking into account the adjacent-channel crosstalk, and the nonlinear effect generated by four-wave mixing at around the zero-dispersion wavelength. Superdense WDM transmission is also performed experimentally using 25-GHz channel-spaced, 15-GHz wide, up-to 156-Mb/s signals through up to 120 km of dispersion-shifted fiber.

Experimental investigation of injection locking of fundamental and subharmonic frequency-modulated active mode-locked laser diodes

Narrow linewidth and stabilized light injection is employed to reduce the phase noise and stabilize the frequencies of individual teeth of an active mode-locked laser diode (ML-LD) which is modulated by both fundamental and subharmonic frequencies of the cavity free-spectral range (FSR). We demonstrate accurate frequency control of the ML-LD using an injection seed light with linewidth of less than 100 kHz and frequency of exactly 193.1 THz; the light is generated by offset-locking to an absorption line of H/sup 13/C/sup 15/N. The teeth of the injection-locked ML-LD are anchored at 193.1 THz and are generated with 25- or 12.5-GHz sparing at the fundamental or subharmonic modulations, respectively, The teeth also have the linewidth of less than 100 kHz and the absolute frequency accuracy of better than 10 MHz. These values are the same as those of the injection seed light. The residual phase noise of the injection-locked ML-LD, estimated from the self-heterodyne spectrum, is less than 1 kHz at 20 dB down.

A quaternary amplitude shift keying modulator for suppressing initial amplitude distortion

This paper proposes a quaternary amplitude-shift-keying (4ASK) modulation circuit that suppresses amplitude distortion of the transmitting 4ASK signal. The performance of the proposed circuit is quantitatively verified through numerical calculation in comparison to a conventional alternative. The feasibility of the proposed circuit as integrated in a lithium niobate substrate is also demonstrated: the suppression of amplitude distortion is successfully demonstrated and minimum sensitivity of the transmitted 4ASK signal is 1.7 dB better than that offered by the conventional circuit.

Accurate frequency control of a mode-locked laser diode by reference-light injection.

Injection locking is employed to narrow the spectrum linewidth of individual modes of an active mode-locked laser diode (ML-LD). The multiple modes of the injection-locked ML-LD lie over 3.0 THz with 25-GHz spacing at 30 dB down; their linewidth and stability, ~25 MHz, are nearly the same as those of the master laser. We also demonstrate the accurate frequency measurement of laser diodes stabilized to molecular (H(13)C (15)N ,(13)C(2)H (2)) absorption lines by use of the injection-locked ML-LD.

OTN technology for multi-flow optical transponder in elastic 400G/1T transmission era

We study the multi-flow optical transponder from the viewpoint of OTN. Rate flexible OTU and multiplexing hierarchy for the elastic network are studied in detail and the required OTN standard extension is elucidated.

A Study on the Correlation between QoE of 4K Super High Definition Video Streamings and QoS of Network

Realtime video streaming is one of the most impor- tant tool for the computer supported collaborative workspace (CSCW). CSCW requires bi-directional or many-directional video exchanging. The delay or jitter caused by network quality is easily affecting application or users of CSCW. The quality of experience (QoE) of CSCW with video streaming over IP networks depends on the quality of network. It is important to consider the relationship between the QoE of video streaming and quality of service (QoS) of the network in order to achieve high quality CSCW services effectively. Then we can define the suitable parameter of networks for the applications. The goal of this research is to establish the evaluation method of the correlations between the QoE of CSCWs and QoS of networks to obtain the optimal real-time communication system design. In this paper, we propose a method to measure the correlation between the application and network QoS with precise packet monitoring environment. The result shows that micro-second resolution helps a lot to capture the precise behavior which effects the codec systems performance.

Optical carrier supply module applicable to over 100 super-dense WDM systems of 1000 channels

This paper presents a prototype of an optical carrier supply module (OCSM) with a 12.5-GHz spaced 256-channel WDM carrier generator applicable to over 100 super-dense WDM systems and describes its scalability to 1000 channels.

Wavelength selectable photonic transport system applicable to unequal channel spacing

A photonic transport system with optoelectronic wavelength converter applicable to unequal channel spacing is demonstrated. A compact 8/spl times/8 wavelength selective switch and a polarization independent electroabsorption modulator are developed for designing the large-scale system.

12.5-GHz-spaced super-dense WDM ring network handling 256 wavelengths with tapped-type OADMs

We demonstrated a two-fiber WDM ring network that handles 12.5-GHz-spaced 256 wavelengths using a tapped-type optical add drop multiplexer (OADM) consisting of small-scale 12.5-GHz-spaced arrayed waveguide gratings (AWGs) and BPFs. The feasibility of the network employing the prototype OCSM was shown by transmission experiments.