By Mike Downing
In an effort to enable bandwidth-on-demand for remotely provisioning bandwidth through metro WDM infrastructures, Bandwidth9 (Fremont, CA) has recently announced plans to introduce a line of tunable optical transmission modules.
According to Tim Richardson, executive VP of business development for Bandwidth9, the initial product will be an integrated evaluation card that consists of a broadly tunable, directly modulated, semiconductor laser source, an erbium-doped fiber amplifier (EDFA), and the hardware, firmware, and programmable logic to provide repeatable, tunable wavelength and power control. The card can be provisioned remotely through a graphical user interface (GUI). The laser source can be directly modulated at speeds up to SONET OC-48 or SDH STM-16 data rates.
In addition, these tunable modules will enable spares that can replace as many as 60 fixed-wavelength laser sources in metro systems. The tunable modules will be capable of covering either the C-band (1530-1564 nm) or the L-band (1580-1620 nm) and will be available for select customers by year-end. Richardson said that equipment manufacturers and carriers have already expressed interest.
"Not only did we want to develop a 1500-nm VCSEL device [which the company also recently announced], we also wanted that device to be tunable," said Richardson. He says that the tunable devices will go a long way toward eliminating the need to keep dozens of fixed-wavelength spares on hand.
"Tunable devices are a disruptive technology," he says. "This will profoundly affect how bandwidth providers do business. It will also reduce bandwidth costs."
Richardson sees the direct modulation feature as a major plus. "Every signal is a modulated signal," he said. "But there is a difference. Most devices, whether they're tunable or fixed-wavelength devices, involve external modulators. In fact, there is an entire industry making external modulators for these devices."
"But an external modulator is nothing more than an expensive shutter," he continued. "A laser emits light, and the shutter pulses the output. The speed of the shutter determines the data rate. But here's the distinction: Our device does not don't require the external modulator because we modulate the device electrically."
Richardson claims this breakthrough makes the architecture smaller and less expensive. "And external modulators are expensive," he said. "They are $1,000-plus devices in their cheapest form, and they can cost several thousand dollars in their more advanced forms."
Eventually, Richardson believes that the cost of tunable devices will drop until fixed-wavelength devices become obsolete. "Every card will be tunable," he said. "That's when new networks can be created...photonic switch networks that are basically bandwidth-on-demand. Wavelength assignments can be routed dynamically. The tunable cards will enable this shift."