Search

Integration of 25-GHz-spacing wavelength monitors into industry standard butterfly laser modules are successfully achieved through the use of a unique optics. The 2-thermoelectric cooler (TEC) design enables independent temperature control of the laser diode and the wavelength monitor, hence eliminating the temperature dependence of the etalon as well as wavelength variation due to temperature variation and aging. As a result of the independent temperature control, narrowband tuning is easily achieved. Results from a series of thorough wavelength stability tests show that the wavelength variation of these laser modules are well within the ITU-T recommended requirement for 25-GHz channel-spacing dense wavelength-division multiplexing (DWDM) applications throughout 25 years of usage.

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.

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.

To identify the nature of neurotransmitters acting on the smooth muscle cells of the proximal urethra and the electrical activity underlying the mechanical responses to nerve stimulation.The electrical activity of longitudinal strips of proximal urethra obtained from male rabbits was recorded with microelectrode and double sucrose-gap techniques. Intramural nerves were stimulated with 200 microseconds pulses. Drugs which selectively affected neurotransmission were added to the perfusing fluid.The mean resting potential of smooth muscle cells was -39 mV and they had infrequent spontaneous action potentials. The frequency was increased by noradrenaline without depolarization; ATP produced depolarization with increased action-potential frequency. Small (or = 16 mV) spontaneous depolarizations and hyperpolarizations could be recorded from50% of cells; large (or = 40 mV) hyperpolarizations also occurred. Electrical field stimulation evoked excitatory and inhibitory junction potentials (EJPs and IJPs). Most EJPs reached a maximum within 500 ms, decayed with a time-constant of 200-300 ms and were blocked by alpha, beta-methylene ATP. IJPs had a latency of1 s and showed much variation in amplitude and duration. IJPs could still be recorded in the presence of N-nitro-L-arginine methyl ester (L-NAME). In the double sucrose-gap, depolarization and associated contraction were reduced by alpha, beta-methylene ATP. Further reduction occurred with phentolamine and the remaining response was blocked by atropine. A large hyperpolarization could occur in response to a single stimulus but this decreased progressively with repeated stimulation. The hyperpolarization was partially blocked by L-NAME.The proximal urethra receives excitatory innervation involving three neurotransmitters, i.e. ATP, acetylcholine and noradrenaline, and inhibition is associated with hyperpolarization which results at least in part from action of non-nitrergic nerves.

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.

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.

The use of YAG welding and soldering techniques for fixing optical components made it possible to achieve average wavelength drift of less than /spl plusmn/2 pm during tests, which can be applicable for 25 GHz channel spacing DWDM system.

We have fabricated the thermally controlled, widely tunable laser module using matrix DFB laser. To realize high output power and wide tunability simultaneously, 12 DFB lasers were integrated in the form of 2 /spl times/ 6 matrix with low loss 1 /spl times/ 6 multi mode interferometer coupler and semiconductor optical amplifier. Optimizing lasing wavelength of the DFB lasers, stable single mode operations with side mode suppression ratio of over 40 dB were obtained. The module has shown excellent characteristics, such as high polarization maintaining optical fiber coupled power over 30 mW and wide tunability over 37 nm.

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.

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.

The thermally-controlled laser module, integrating 12 distributed feedback (DFB) lasers in the form of a 2×6 matrix to realise both high output power and wide wavelength tunability, has been fabricated. The module has shown excellent characteristics, such as high fibre coupled power over 30 mW and tunability over 37 nm.