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Simple switching scheme of frequency with precise feedback control of robust wavelength locker has been presented for a short-cavity DBR laser array. Switching time was less than 13 µsec within +/-2.5GHz from ITU grid. IntroductionNew network technologies such as optical packet switching and optical burst switching will be introduced to next generation network, to accommodate increasing traffic of internet services. These technologies realize transparent optical routing. For the optical burst switching, agile tunable wavelength converter is indispensable to avoid burst contention in optical region [1]. For this use, tuning speed of tunable lasers should be around a few microseconds, however, commercial tunable lasers based on multi-section DBR laser can not guarantee tuning speed of sub milliseconds. Experimentally, wavelength switching in the order of nanoseconds has been reported. under feed forward control without wavelength monitoring, however, both wavelength stability and reliability are not ensured over long period time because wavelength was affected by thermal relaxation process in the laser module. In addition, multi-section DBR lasers have been used, therefore, control circuits are considered to be rather complicated. There are only a few reports on fast wavelength locking for tunable lasers [2][3][4]. In this paper, we show simple control scheme for a stable wavelength switching by using both a short-cavity DBR tunable laser and a built-in wavelength locker packaged in a standard butterfly package, resulting in fast and stable wavelength switching time of approximately 10 microseconds. A short cavity DBR laser and integrated wavelength lockerWe have reported a short-cavity DBR tunable laser which realizes continuous wavelength tuning by changing only one DBR current without phase control. Integrating six lasers (DBR and gain sections), an MMI coupler and an SOA in one chip, continuous tuning range of 21 nm had been achieved as shown in fig. 1 [5]. Robust and compact laser module with built-in wavelength monitor was also developed [6]. In fig. 2, the laser module consists of the DBR laser array, a collimator lens, an optical isolator, a beam splitter, a Fabry-Perot etalon, and two photo-diodes. The hexagonal-shaped beam splitter splits collimated beam in three portions for wavelength monitoring, power monitoring, and fiber output. This monitor ensures the stable wavelength on the ITU grid over 30 nm. The module is potentially high-reliable packaging by the use of soldering and laser welding techniques. Dynamic switching characteristics of this module are investigated assemble onto control electronics.

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We have fabricated wavelength selectable lasers loaded with hgh-efficiency TiPt heater. Wavelength tuning by use of comb-shaped heater structure on DFB lasers array, temperature arise of SOA was suppressed, resulting in drastic improvement for the variation of optical output power at high temperature. Tuning range of 9.8 nm for wavelength selectable laser integrating four DFB lasers was realized with heater power consumption of as low as 0.36W.

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