Hideyuki Nasu

Recent advances in DFB lasers for ultradense WDM applications

State-of-the-art distributed feedback (DFB) laser modules integrated with a wavelength monitor are presented that provide excellent wavelength stability. By adopting unique and compact configuration, wavelength deviations of as small as a few picometers have been achieved. The laser modules are improved also in the scope of high power, high reliability, and wavelength tunability. Reliability test results of the DFB laser diodes and modules confirm a sufficiently long lifetime of more than 25 years and a small wavelength drift of less than /spl plusmn/3 pm. The developed laser modules are fully applicable to ultradense wavelength-division multiplexing applications with the current narrowest channel spacing of 25 GHz.

Short-Reach Optical Interconnects Employing High-Density Parallel-Optical Modules

This paper reviews the high-density parallel-optical modules for use in board-to-board application in optical interconnects and describes their application, mechanical sizes, electrical-pluggable interfaces, optical-pluggable interfaces, transmission performance, and power consumption. Since board-to-board optical interconnects require a high data rate per channel of at least 10 Gb/s/ch, a power consumption of not more than 10 mW/Gb/s/link, and high reliability based on massive volume requirement, the usage of 1-μm wavelength range using InGaAs high-efficient semiconductor devices is promising to meet these requirements.

Ultrahigh wavelength stability through thermal compensation in wavelength-monitor integrated laser modules

By taking into consideration the drift of the wavelength-discrimination curve induced by variations in etalon temperature, compact 25-GHz-spacing wavelength-monitor integrated laser modules that exhibit extremely small wavelength drift of less than 5 pm over a wide range of operation conditions, and throughout the lifespan of the laser module, are being developed.

25-GHz-spacing wavelength-monitor integrated DFB laser module for DWDM applications

For the first time, a 25-GHz-spacing wavelength monitor is successfully integrated into an industry standard 14-pin butterfly laser module through the use of a unique configuration. The temperature-induced wavelength drift of these wavelength-monitor integrated laser modules for a case temperature ranging from -5/spl deg/C to 70/spl deg/C is less than /spl plusmn/10 pm.

Sn–Ag–Cu Solder Reflow-Capable 28-Gb/s × 4-Channel High-Density Parallel-Optical Modules

This paper describes a unique solution to the next-generation high bit-rate and high channel-density parallel-optical links whereby the size of parallel-optical modules would have to be considerably reduced. Since the main problem concerning the size of optical-to-electrical conversion part is associated with the mounting of the parallel-optical module to the printed-circuit-board (PCB), this paper puts forward a remarkably compact parallel optical-module design that can be soldered directly onto the PCB. That is made possible by the high temperature tolerance of 250 °C required for Sn-Ag-Cu solder-reflow process. The miniature parallel-optical module measures only 10.5 mm in length, 6.5 mm in width, and 1.5 mm in height. The resulting parallel-optical modules are capable of four-channel error-free parallel pseudo-random binary sequence 231-1 transmission at 28 Gb/s without using clock and data recovery as well as feed-forward error correction (FEC); hence, these parallel-optical modules are applicable in next-generation high-density 100 Gb/s Ethernet applications that use FEC.

Detailed investigation on reliability of wavelength-monitor-integrated fixed and tunable DFB laser diode modules

A highly reliable integration of a wavelength monitor (WM) in an industry standard 14-pin butterfly package has been successfully achieved by using soldering and YAG welding techniques. Mechanical integrity and endurance tests for fixed and tunable distributed-feedback (DFB) laser diode modules (LDMs) were performed according to an extended Telcordia GR-468-CORE in order to appreciate the fixtures of the WM part composed of a prism, a Fabry-Pe/spl acute/rot etalon, power, and WM photodiodes. Wavelength and a fiber output power were evaluated as a function of duration time for each test. Incident light angles change against an etalon and an optical coupling deviates due to the separation between a laser diode part and a WM part for tunable DFB LDMs. The two occurrences have a profound influence on wavelength drifts. It was found that the wavelength drifts were less than /spl plusmn/5 pm under mechanical and thermal stresses for both types of DFB LDMs. It was also confirmed that the coated and mounted etalon itself was also highly reliable under thermal stresses. These results show that the WM-integrated fixed and tunable DFB LDMs were fully applicable to next-generation dense-wavelength-division-multiplexing (DWDM) systems of 50- and 25-GHz channel spacing.

A Record 1-km MMF NRZ 25.78-Gb/s Error-Free Link Using a 1060-nm DIC VCSEL

We report successful achievement of a record long distance error-free transmission of 1000-m 50-μm-core multimode fiber (MMF) in a non-return-to-zero 25.78-Gb/s modulated vertical cavity surface emitting laser-based optical link using four-channel miniature parallel-optical modules. The optical power is centralized within the core of MMF by an active alignment assembly. The restricted launch condition gives a very high effective modal bandwidth (EMB) of >9 GHz · km based on the calculations and the required performance data specified in TIA-FOTP-220. An EMB of 11.5 GHz · km provides a very good agreement between the calculated and measured power penalty characteristics. Such a long distance low-cost MMF link, operating at 1060-nm wavelength is potentially an alternative solution to PSM4.

A highly stable and reliable wavelength monitor integrated laser module design

Three existing wavelength monitor integrated laser module designs are evaluated. The shortcomings of these designs are resolved by a unique design that eases alignment tasks and greatly enhances the wavelength stability and the wavelength tunability. For example, the wavelength drift over case temperature is 16 times smaller than the best result of previous reports. With the incorporation of thermal compensation, the temperature-induced wavelength drift of the etalon is eliminated. In anticipation, this design enables a worst overall wavelength-drift of 4.41 pm after 25 years of usage to be achieved.

25 GHz-spacing wavelength monitor integrated DFB laser module using standard 14-pin butterfly package

A 25 GHz-spacing wavelength monitor integrated DFB laser module has been successfully fabricated using standard 14-pin butterfly package. By employing separate temperature control for the LD and etalon, excellent wavelength locking performance (wavelength drift < /spl plusmn/0.2 pm) has been achieved using a simple analogue circuit.

40 mW over DFB laser module with integrated wavelength monitor for 50 GHz channel spacing DWDM application

We fabricated an over 40 mW DFB laser module with integrated wavelength monitor employing an etalon filter. An evaluation of this module with a simple feedback circuit, showed that the effect of wavelength drift factors, such as the injection current and case temperature, are small enough for 50 GHz channel spacing DWDM applications.