Dense wavelength-division multiplexing (DWDM) offers a great way to boost speed and channel capacity in any fiber-optic system. A laser for each wavelength of IR light is needed to multiplex multiple wavelengths on a single fiber, and lasers generally have a fixed wavelength. At a cost of thousands of dollars each, DWDM systems are very expensive and difficult to justify, not only for the initial cost but also for the dozens of spares needed on hand for repairs.
To the rescue come tunable lasers. Intel's TXN13600 tunable laser transceiver will make DWDM more affordable (see the figure). It also will open the technique to other unique applications, including those where wavelength can be switched on-the-fly. Designed for metro and long-haul fiber network equipment using Sonet/SDH or Ethernet, it accommodates common system rates of 9.95, 10.3, 10.66, 10.71, and 11.1 Gbits/s.
Craig Thompson, marketing director for Intel's Optical Platform Division, says that the carriers can cut their multimillion-dollar budgets by 90% by reducing parts inventories. He added that Intel expects full C-band tunable transciervers to completely displace single-channel units.
The TXN13600 covers the optical C band from 1525 to 1565 nm. It tunes the full range and can be set to any of the 80 standard wavelengths used in DWDM systems. Channels can be selected in 100-, 50-, or 25-GHz increments. Output power is factory-settable from +1 to +5 dBm. And, a thermally variable filter manages this external-cavity laser's tuning.
A wavelength-locking feature perfected by Intel ensures precise and stable tuning across the entire C band. It provides ±2.5-GHz wavelength setting accuracy to minimize crosstalk on 50-GHz spaced DWDM systems. The TXN13600 also features a very low power dissipation of 8 W typical, 11 W maximum. The embedded controller handles wavelength control via an I2C interface.
On the receive side, Avalanche photodiodes and PIN diodes are both available. Also, the receiver features adjustable control of the decision threshold. A unique suppression dither control optimizes link performance without affecting other transmitter characteristics.
The TXN13600 has a 4.1- by 3.5- by 0.53-in. form factor and is 300-pin multisource-agreement compatible. Priced at $7000, samples are available now. Full production quantities are due in the second half of 2004. The laser module alone, the TTX11500, is available with similar specifications. Intel indicates that an L-band version is on the way.