Tunable Lasers - Current Realities and Future Prospects

By Lisa Huff
and
Christine Mulrooney

To achieve the vision of a programmable network, equipment providers are considering the use of tunable components, and more specifically tunable lasers, to allow flexibility that is unavailable today. Tunable lasers have obvious benefits for optical networking systems. Instead of having to maintain an inventory of spares for each channel or port, service providers would be able to stock a few tunable transmitters that could be used to replace failed parts.

Sparing is just one potential application of tunable lasers. More exciting is the prospect of remote service provisioning of the network. This would allow service providers to remotely change the wavelengths utilized by a specific customer to provide "bandwidth on demand." The potential cost and performance benefits of such an approach are enormous. However, the fact is that at present, the reality of tunable lasers lies considerably behind that potential.

Based on recent CIR research, this CIR White Paper sets out the current limitations of tunable lasers and assesses their prospects for the future. As Exhibit I shows, CIR sees considerable growth in this marketplace, although it does not expect to see most of this growth materialize for a few years, by which time tunability will rapidly become a standard feature of many telecommunications lasers.

At this time, there are only two uses for tunable lasers. Tunables are used as temporary replacements for lasers that have failed in a deployed system to keep the equipment running, they are then replaced with a fixed wavelength laser when the correct one is obtained. Tunable lasers are also being used in performance monitoring equipment to monitor several wavelengths at once.

CIR research indicates that most equipment manufacturers are slow to deploy tunable laser technologies. There is general concern about the robustness and long-term reliability of tunable lasers. Today’s tunable lasers have shown good performance but only in the lab environment. Equipment manufacturers believe that today’s products are not ready for broad implementation. Nonetheless, most are actively evaluating tunable laser technologies and are ready to take advantage of these products when they become available.

A certain amount of technological chaos currently exists in the tunable laser market and

CIR believes that for this market to reach its full potential, current technological issues will have to be resolved. In particular, the market will have to determine the importance of the various tradeoffs that are implicit in the tunable laser technologies now being considered. Meanwhile, equipment manufacturers and component suppliers alike are trying to obtain the perfect tunable laser that would address the needs of these growing applications. (See Exhibit II.)

Many tunable laser manufacturers are arduously working at improving the reliability of their devices. All are starting to incorporate integrated wavelength lockers in order to improve stability of the device at each wavelength. Improvements in manufacturing process controls are being realized daily so most components manufacturers are expecting to be in volume production of qualified products by the end of 2001. Among these are Nortel High Performance Optical Components, New Focus, Agility, ADC, Alcatel Optronics, JDS Uniphase, Marconi Optical Components, iolon and Corning. Fujitsu claims it is already in volume production with its devices and they are being incorporated in Fujitsu DWDM equipment.

Nortel has addressed the stability issue by designing its tunable transmitters with integrated wavelength lockers and closed feedback for continuous tuning over the life of the device. Many other manufacturers are starting to use similar techniques in order to assure equipment manufacturers that tunable lasers are viable for system deployment in the long-term.

CIR believes that the technological issues outlined above will take some time to completely address, but once they are, it will open up new applications for tunable lasers. Initial deployment of tunable lasers will be as spares for fixed lasers that fail. But in order to take full advantage of the functionality of these tunable components, the topology and management of the network must change, therefore, CIR sees a relatively slow adoption of the devices over the next few years.

Although equipment manufacturers are not deploying tunable lasers to their full functionality currently, they are excited about the prospects that these components hold. Once the reliability issues are resolved, and CIR has no doubt that this will happen, equipment manufacturers will use them for inventory reduction, performance monitoring as well as dynamic provisioning.

One area in which we see particular potential because of its large size, is the metro market. However, before tunables can be widely used in the metro environment, costs will need to approach that of fixed wavelength lasers. Nonetheless, the metro market has a huge potential for growth and is already the focus of many tunable laser manufacturers. Metro distances are relatively short, therefore, output power does not need to be as high as is necessary for the long-haul market. Cost is a huge consideration in this arena so low cost technology, coupled with automated manufacturing will be key for supplier success.

CIR believes that the future of tunable lasers will also include a transition of vendor focus from component level products to sub-systems. Initially, the lasers will be sold as components for sparing but eventually, they will be sold as tunable transmitters for optical networking equipment designed for wavelength agility to enable flexible and remote service provisioning.

Eventually, most of the tunable laser manufacturers will be selling these components as sub-systems or modules and not laser components – that is, they will be selling tunable transmitters. The main reason for this is that there is no one more familiar with how to control the lasers than the manufacturers themselves and since most of the manufacturers have already taken the time and spent the resources to develop the entire transmitter sub-system, it would be advantageous for equipment manufacturers to take advantage of this. That way equipment manufacturers need not spend time determining how to incorporate the transmitters into the system, component suppliers have already done this for them. The only problem with this is that if component suppliers have different tunable transmitters, equipment manufactures would have to accommodate at least two different designs in order to have a second source.

However, ADC and Agility recently proposed the obvious solution for the second sourcing issue in a multi-source agreement (MSA). The agreement would allow component suppliers to develop tunable lasers using any technology but within a certain footprint and with standard control parameters. In CIR’s opinion, this agreement will do more to enable the market than anything else. The success of this MSA is not only important for tunable transmitters and lasers but also for the future of standardization of optical components. If this agreement is successful, CIR predicts that most other new optical sub-systems will be designed under similar agreements.

CIR will be releasing a report in July 2001,"Tunable Optical Components: A Technologies & Market Assessment", with a full technology and market analysis of tunable components that will include an in depth analysis of tunable lasers. For information on this report contact Robert Nolan at CIR, (804) 984-0245 ext. 15 or e-mail: robert.nolan@cir-inc.com.