O. Kamatani

Ultrahigh-speed clock recovery with phase lock loop based on four-wave mixing in a traveling-wave laser diode amplifier

A new phase lock loop (PLL) is proposed and demonstrated for clock recovery from an ultrahigh-speed time-division multiplexed (TDM) optical signal. A traveling-wave laser-diode amplifier (TW-LDA) is used as a phase detector, and the cross-correlation component between the optical signal and an optical clock pulse train is detected as a four-wave-mixing (FWM) signal generated in the TW-LDA. A timing clock from a TDM signal is extracted as a prescaled electrical clock, and this prescaled clock is directly recovered from a randomly modulated TDM optical signal. A prescaled 6.3 GHz clock is successfully extracted from a 100 Gb/s signal using the timing comparison output obtained as the cross-correlation between the optical signal and a short (<10 ps) 6.3 GHz optical clock pulse train in the generated FWM light. A comparison of the PLL phase noise with a previously reported gain modulation method is also shown, and the possibility of the Tbit/s operation of this PLL is also considered in the experiments.

Optical coherence domain reflectometry by synthesis of coherence function with nonlinearity compensation in frequency modulation of a laser diode

Optical coherence domain reflectometry (OCDR) is proposed by synthesis of the coherence function for high-spatial-resolution diagnoses of optical systems and waveguide devices. By changing the output frequency of a laser diode using its direct frequency modulation characteristic, the coherence function having the shape of a delta function is synthesized. In the basic experiments, the reflectivity distribution is measured successfully by sweeping the position of the peak. Nonlinearity compensation in the direct frequency modulation is experimentally demonstrated in order to improve the resolution. A three-electrode DFB laser diode with wide-frequency tunable range is introduced as the light source. A spatial resolution of 2-4 mm in air is demonstrated. The measurement range flexibility of this method is confirmed in the experiments. >

Optical coherence domain reflectometry by synthesis of coherence function

We have proposed an optical coherence domain reflectometry by synthesis of coherence function (OCDR), for high spatial-resolution measurements of optical waveguide devices. We present the principle of the OCDR and the recent experimental results of the OCDR with spectrum spacing control of many lines. A three-electrode DFB laser diode with wide frequency tunable range is used as the light source to improve the resolution. The spatial resolution of 3 to approximately 4 mm in air has been obtained. Furthermore, overall effects of the performance deterioration factors are theoretically considered.

100-Gbit/s optical TDM add/drop multiplexer based on photonic downconversion and four-wave mixing

Summary form only given. Future ultrahigh-speed optical transparent networks require optical time-division multiplexed (TDM) signal processing nodes that can control optical short pulses of several picoseconds. We have proposed an add/drop multiplexer based on optical wavelength conversion by four-wave mixing (FWM), and confirmed its operation with synchronized signals. In this report, we propose an optical TDM add/drop multiplexer using a phase-lock loop timing extraction circuit and demultiplexer based on photonic downconversion for a stable add/drop operation with a simple configuration.

200 Gbit/s, 100 km TDM Transmission using Supercontinuum Pulses with Prescaled PLL Timing Extraction and All-Optical Demultiplexing

New types of optical short pulse sources are now being tested in high-speed optical transmission experiments such as mode-locked fiber ring laser (ML-FRL) [1]–[4] and supercontinuum (SC) [5]. In this report we demonstrate successful 200 Gbit/s optical time-division-multiplexed (TDM) transmission experiments using 2.1 ps optical pulses generated by SC driven by ML-FRL. We confirmed successful operation of prescaled PLL timing extraction and all-optical demultiplexing at 200 Gbit/s.

All-optical time-division-multiplexing of 100-Gbit/s signal based on four-wave mixing in a semiconductor laser amplifier

Ultrahigh-speed modulation of optical pulses is one of the key technologies in time-division multiplexed (TDM) optical transmission at 100 Gbit/s region. Especially, all-optical modulation combined with ultrahigh-speed optical clock source will realize an all-optical transmitter over 100 Gbit/s. We have proposed all-optical modulation using four-wave mixing (FWM) in fiber and confirmed its basic operation at 100 Gbit/s. In this report, we present successful experimental results of all-optical modulation using FWM in semiconductor laser amplifier (SLA). A 100-GHz optical clock was all-optically modulated by two independently modulated 10-Gbit/s signals to produce a TDM signal with 10-ps time interval as a FWM component. Error-free operation was confirmed for both channels.