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We apply a newly developed 2-μm distributed Bragg reflector (DBR) laser to CO spectroscopy. We achieve mode-hop free wavelength tuning over 4 nm by sweeping the DBR current and phase control current, simultaneously. The sensitivity of this laser spectroscopy system is better than 5 × 10, which is the noise level, and means that a CO concentration of 400 ppm can be detected with a path length of 1 m. We confirm that the DBR laser in the 2-μm region maintains a wide tunability of 4 nm even when rapidly swept at a scan rate of 10 kHz. [ABSTRACT FROM AUTHOR]

An optical phase‐sensitive amplifier (PSA) has the potential of low‐noise optical amplification. A frequency non‐degenerate PSA (ND‐PSA) can amplify arbitrary modulation formats including higher‐order QAM. The ND‐PSA requires a co‐propagating phase conjugated light (idler light) that has been conventionally created with an optical phase conjugator at the transmitter side. We propose a transmitter configuration using simultaneous signal generation of both a signal and its idler by double‐sideband modulation for transmission systems with ND‐PSAs. The proposed scheme provides a simple configuration with a single Mach–Zehnder amplitude modulator without optically creating the idler light. We performed experiments using 16QAM, 32QAM, and probabilistically shaped 256QAM signals. As a result, a phase‐sensitive amplification with each modulation format was successfully demonstrated using the proposed transmitter configuration. [ABSTRACT FROM AUTHOR]

This paper proposes a tuning technique to optimize the input power of a cross-phase modulation wavelength converter (XPM-WC). The focus is on an output signal whose wavelength is the same as the input signal. The optimum input power can be easily set by keeping the output signal (not converted signal) power constant. Input continuous-wave (CW) power should be increased or decreased with increasing or decreasing input signal power so that the output signal power stays fixed at the optimum level. Observing the eye pattern of the converted signal is unnecessary. Wavelength conversion from a fixed optical channel to a random one (30 channels with 100-GHz spacing) is successfully demonstrated by using this technique. A low-power penalty (<1dB) and a low-power fluctuation (<1dB) were confirmed in all optical channels. An XPM-WC unit containing a variable CW light source and its level controller were fabricated and simultaneous and automatic operation was confirmed. [ABSTRACT FROM PUBLISHER]

We achieved successful low-input-power (-10 dBm) wavelength conversion at 10 Gb/s by using a hybrid integrated cross-phase modulation wavelength converter (XPM-WC). The input CW power was also -10 dBm and the total current was only 215 mA, and no signal preamplifiers were used. From the relationship between the eye-opening ratio and the injection current to the SOA, we clarified the optimal current condition for low-input-power operation. The XPM-WC consists of a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA), which is mounted on a planar lightwave circuit (PLC) platform. We also fabricated an 8-slot unit. XPM-WC modules are inserted in every slot and can operate independently. Stable and uniform low-input-power operation is confirmed in all slots. [ABSTRACT FROM PUBLISHER]

We have successfully fabricated a 100-GHz spacing 8-channel light source using hybrid integration technologies based on planar lightwave circuits (PLCs). The light source was composed of UV-written Bragg gratings and laser diode (LDs) on PLC platforms. To adjust the Bragg wavelength to the ITU-T grid, we used a precise phasemask with eight different pitches. Moreover, to suppress temperature-dependent mode hopping, we tuned the longitudinal mode wavelength so that it became stable by photosensitively modifying the waveguide refractive index in the cavity, which we achieved using an ArF excimer laser, in addition to inserting silicone in the cavity. As a result, we obtained eight lasing wavelengths controlled to those of the ITU-T grids and optical powers of more than 1.5 mW at an injection current of 80 mA without any temperature dependent mode hopping in the 8-channel light source. We also confirmed direct modulation at 2.5 Gb/s in every channel and we showed that we could modulate two adjacent channels simultaneously without any interference effect. These results show that the compact PLC-type integrated light source is promising for use in WDM systems. [ABSTRACT FROM PUBLISHER]

We propose an approach to optical wave field spot-size conversion that uses a waveguide structure. An optical wave field is decomposed with a Hermite-Gaussian basis, and we describe its motion with partial differential equations for the field radius and center parameters derived from the propagation of the lower order components. We use the equations to design a spot-size conversion waveguide structure for expanding and reducing a field spot as an example in a quasi-single-mode optical waveguide. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate an integrated external-cavity laser (ECL) with a novel configuration designed to suppress temperature-dependent mode hopping. The laser cavity is composed of a spot-size converter integrated laser diode (SS-LD), a UV-written grating, and silicone-filled grooves on a planar lightwave circuit (PLC). The silicone is used to compensate for the difference between the temperature coefficients of the SS-LD and the silica waveguides. We calculate theoretically the temperature interval of the mode hopping in the ECL to optimize the length of the silicone-filled grooves. We fabricated test and practical lasers with the proposed configuration using PLC hybrid-integration technologies. With the test laser, we confirmed stable single-mode oscillation and a large increase in the mode-hopping temperature interval for both static and dynamic operation. We obtained a low threshold of 15 mA, an optical power of 1.0 mW at 25°C, and an injection current of 60 mA. In the practical laser, which we additionally integrated with a front monitor photodiode, we realized auto power control with mode-hopping-free operation from 18°C to 56°C. These results indicate the good performance levels of our proposed laser. [ABSTRACT FROM PUBLISHER]

A novel bit rate and format independent differential group delay monitoring method using a hybrid-integrated wavelength converter is proposed. This method could work at more than 100 Gbit/s, and its feasibility was successfully confirmed through the demonstration of 40 Gbit/s PMD compensations with RZ and NRZ format. [ABSTRACT FROM AUTHOR]

The authors successfully fabricate a 100-GHz spacing eight-channel light source integrated with gratings and laser diodes on a planar lightwave circuit platform. They obtain mode-hopping free-single mode oscillations, precisely controlled wavelengths, and sufficient output power of more than 1.5 mW at 80 mA. [ABSTRACT FROM PUBLISHER]

We developed a compact 16-ch optical wavelength selector (OWS). Our OWS is composed of two arrayed-waveguide gratings (AWG's) and an optical gate array (OGA) integrated on a single PLC platform by using the hybrid integration technique. We successfully obtained lossless operation with an extinction ratio of better than -45 dB for all wavelength channels. We also obtained a switching time of less than 1 ns. These excellent characteristics are the same as those of a previously reported OWS fabricated using PLC-PLC direct attachment [ABSTRACT FROM PUBLISHER]

We propose a silica-based 2×2 thermooptic switch using heat insulating grooves and trenches on a Si substrate to reduce electric power consumption. The switching power of a fabricated switch was successfully reduced to 135 mW, less than 1/3 that of a conventional switch. No detrimental effect on optical characteristics was observed: we obtained the insertion loss of 1 dB, the extinction ratio of better than 30 dB and no polarization dependency [ABSTRACT FROM PUBLISHER]

An integrated external cavity laser (ECL) using planar lightwave circuits (PLCs) with a higher than usual refractive index contrast has been successfully demonstrated. The small modefield of the PLCs enables use of a laser diode without a spot-size converter and eliminates the need for a Si terrace structure. The oscillation characteristics of the ECL are as good as those of a conventional ECL with a lower contrast. [ABSTRACT FROM AUTHOR]

A novel optical bandpass filter is proposed that consists of an arrayed waveguide grating pair and an optical slit. A 200 GHz cyclic and 40 GHz passband optical filter using the proposed configuration, which is useful for WDM single sideband filtering, is successfully demonstrated. [ABSTRACT FROM AUTHOR]