Akihito Otani

Low-Time-Jitter Short-Pulse Generator Using Compact Gain-Switching Laser Diode Module With Optical Feedback Fiber Line

On the basis of a self-pulse feedback mechanism, an ultralow-time-jitter and flexible repetitious rate optical pulse generator module with a simple and compact design was developed. Using a compact design self-seeding distributed feedback laser diode module, a low time jitter pulse on the order of sub-picoseconds was successfully observed within any modulation frequency range from 1 to 2 GHz. A pulse compression technique based on the nonlinear effect in optical fiber was used. A pulse width of 1.9 ps and a jitter of 0.5 ps were obtained with neither waveform degradation nor jitter increase.

All-optical sampling using cross-absorption modulation in electroabsorption modulator for optical performance monitor

All-optical sampling is experimentally demonstrated using cross-absorption modulation in an electroabsorption modulator. A clear eye opening with 7-ps temporal resolution was obtained by optimizing the pump pulse.

High-dynamic-range measurement of millimeter-wave amplifier using 140-GHz fundamental mixer

Analysis and measurement of radio signals above 60 GHz requires connection of an external mixer to a commercial spectrum analyzer. In this setup, in addition to the actual frequency components, unwanted multiple response generated by the external mixer are also observed simultaneously, making it difficult to observe the actual frequency components. Furthermore, the signal components are easily buried by measuring instrument noise due to the poor mixer conversion efficiency, causing difficulties in observing very low power signals. This paper presents the results of some tests and trials of a 140-GHz fundamental mixing test system with potential for high-dynamic range measurements and small unwanted multiple response compared to measurements using previous harmonic mixers. The results are the first to demonstrate a 20-dB or higher dynamic range as well as excellent wideband suppression of multiple response compared to measurements using harmonic mixers.

Double pulse pumping on all-optical sampling using electroabsorption modulator

Double-pulse pumping improves the temporal resolution of cost-effective all-optical sampling using an electroabsorption modulator. A shortened sampling gate width was demonstrated using two double-pulse generation methods.

High sensitive optical sampling oscilloscope simultaneous coverage of both C and L bands

An optical sampling oscilloscope with SFG conversion efficiency as high as 15 times that of KTP, while simultaneously covering both the C and L bands, is demonstrated for the first time.

Demonstration of GMPLS lightpaths diagnosis using an all-optical sampling-based Q-factor Monitor in a network testbed

An all-optical sampling-based Q-factor monitor applicable to multi-bitrated and formatted signals was successfully demonstrated in a network testbed. Quality of GMPLS lightpaths could be diagnosed correlating the actually measured BER.

Chromatic dispersion measurement of EDFA using optical sampling oscilloscope

Summary form only given. In this report, we directly measured relative group delay time of a highly Er-doped EDFA (Er-doped fibre amplifier). (MFD: 6.9 /spl mu/m, Er/sup 3+/ density: 1760 ppm, Al density: 13800 ppm, EDF length: 20 m) under 1480-nm pumping for the first time, to our knowledge, using an optical sampling oscilloscope and an optical short-pulse generator. We also derived its dispersion.

Novel Tunable Filter for Millimeter-Wave Spectrum Analyzer Over 100 GHz

Rapid progress in millimeter-wave wireless communication technologies requires accurate spectrum analysis in the frequency domain over 100 GHz. A tunable preselection filter is a key device in building such a spectrum analyzer. This paper proposes a new tunable filter as a preselector in the frequency range from 110 to 140 GHz. The filter was designed using a commercial electromagnetic simulator and two prototypes were evaluated. The first proved the tuning function in the working range but had a large insertion loss of . The second with various structural and manufacturing improvements achieved both tunability and insertion loss of <;10 dB.

Reduction of insertion loss in millimeter-wave tunable filter over 100 GHz

Rapid advances in millimeter-wave wireless communication technologies require accurate spectrum analysis in the frequency domain over 100 GHz. A tunable pre-selection filter is a key device in building such a spectrum analyzer. We have prototyped a new tunable filter in the frequency range from 110 to 140 GHz, but it suffered significant insertion losses around 116 and 140 GHz. This paper clarifies structural causes of these losses and presents the correct dimensions of the filter. Computer simulation of the redesigned filter gives reduced and flattened insertion loss in the working range.

A Simple Synchronization Method for Optical Sampling Eye Monitor

A simple software synchronization method based on spectral interpolation is proposed for an optical sampling eye-waveform monitor. A clear eye diagram was reconstructed successfully from an asynchronously sampled signal using a passively mode-locked fiber laser. The timing jitter of the reconstructed eye diagram was measured to quantify synchronization accuracy. The 0.0016 UI increase in rms timing jitter caused by synchronization error is negligible.