A single tunable laser module can serve as a backup for multiple channels, so that fewer transponders need to be stocked as spares. In other words, the bill for maintaining and managing the inventory for WDM system spares can be steep, especially for high-speed systems with lots of channels. Their prices vary, depending on their reach and data rate, but can go as high as $20 000 for a long-haul OC-192 (10-Gb/s) unit. These devices therefore account for a high percentage of total component costs in an optical network. A 176-wavelength system uses one laser per wavelength, and must store 176 additional transponders as spares to deal with failures. Known as wavelength-division multiplexing (WDM), this process greatly expands the capacity of fiber-optic communications systems, making them one of the most important parts of the foundation on which the Internet rests.Ĭurrently, WDM transponders, which include the laser, modulator, receiver, and associated electronics, incorporate fixed lasers operating in the near-infrared spectrum, at around 1550 nm. Today, single fiber-optic strands carry multiple wavelengths of infrared radiation across entire continents, with each wavelength channel carrying digital data at high bit-rates. Tunable lasers also make it easy to add or delete bandwidth by remote control-with no need to dispatch a service technician-thereby opening the door to a variety of new on-demand services. Why all the excitement? Replacing 80 or 160 units with one or a few laser types simplifies inventory management. One month later, in June, Nortel Networks Corp., Brampton, Ont., Canada, acquired Coretek Inc., the Wilmington, Mass., company, for around $1.43 billion. In May 2000, for example, ADC, Eden Prairie, Minn., spent $872 million to buy Altitun AB, Kista, Sweden, one of the first companies to offer a tunable laser product for telecommunication applications. Both have already announced products for the tunable laser market.Īt the same time, some of the largest optical communications companies have begun investing heavily in the technology, both by funding in-house R&D and through acquisitions. Some of the light exits through the half-silvered mirror.Ī couple of the more successful start-ups are Agility Communications Inc., Santa Barbara, Calif., which received a total of over US $168 million, and Bandwidth9, Fremont, Calif., which received some $110 million in funding over the last two years. The photons bounce between the mirrors at the ends of the ruby rod, triggering ever more stimulated emissions. As some electrons in the rod spontaneously drop from this high-energy level to a lower ground state, they emit photons that trigger further stimulated emissions. When optically "pumped" by light from the flash tube, the ruby rod becomes a gain medium with a huge excess of electrons in high-energy states. Principle of Operation: The operation of a ruby laser illustrates the basic lasing principle.
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