LaserComm - Optimising Performance for Long Haul
1st February 2002
Interview with Mark Barratt, VP Business Development and Product Planning.
OpticalKeyhole.com and the Optical Networks Daily newsletter conduct interviews on the basis of readership interest only. They are not paid for by the participating companies, nor is there any swap for newsletter subscriptions or advertising.
Introduction
LaserComm is a privately funded company founded in 1998, it is headquartered in Plano, Texas, and has a research and development facility in Tel-Aviv, Israel. LaserComm has to date raised $56 million through three rounds of funding.
The company is a supplier of broadband optical components and modules to system vendors and service providers. To date LaserComm has launched one product, the Hi-Mode DMD. This device increases the capacity and reach of optical transmission networks by controlling signal dispersion. The device is designed to optimise performance of high capacity and long distance 10 Gbit/s networks, and is expected to pave the way to rollout of 40 Gbit/s systems.
Optical components industry
Discussing recent developments in the optical communications industry, and start-up companies such as LaserComm, Mark Barratt noted that optical component companies have made significant technological strides over the past five years, with much of this innovation coming from the start-up community.
Commenting on the factors behind this, Mr Barratt said, "I think that a major factor here was the paradigm shift in the optical market to system vendors buying-in externally developed components. It also illustrates the beauty of the venture capital system in the U.S., which allows innovative start-up companies to realise their full potential. The first factor meant that there were buyers in the market for these start-up companies' innovative products."
Innovation and technology
LaserComm is a company sharply focused on technology and innovation. Discussing the company's strategy, Mark Barratt said that this focus is crucial for a company playing in the optical components sector, "The components sector is different from the systems sector. In the systems sector companies can differentiate themselves by application or engineering. In the components sector, differentiation is by innovation in technology. Following from there, you also need to be able to manufacture the product efficiently and to have a market for that product."
Discussing LaserComm specifically, Mr Barratt stated his belief that LaserComm does have a truly innovative product, he noted, "LaserComm clearly has a differentiator here. That is one of my main reasons for joining the company."
Chromatic dispersion management
LaserComm's activities in the high-order mode optics field have led to the development of a solution to a genuine problem in optical transmission networks, and one that is set to become more prolific. In the area of chromatic dispersion, there have been no commercially viable broadband innovations since the development of dispersion-compensating fibre. Bell Labs investigated the use of high-order mode systems in the early 1990's, but was unable to produce a commercial product. LaserComm's chromatic dispersion management device is claimed as an innovation in this field.
The challenge of chromatic dispersion has influenced the design of transmission fibre. Dispersion-shifted fibre was designed with the zero dispersion point in the 1550 nm operating band of the fibre - to effectively eliminate dispersion. This solution proved adequate until DWDM systems were developed. The advent of DWDM brought with it the need for a degree of dispersion in order to avoid interference between channels. However, this dispersion has to be carefully controlled to prevent signals running together, resulting in bit errors. This requirement led to the development of non-zero dispersion shifted fibre (NZDSF).
LaserComm's product effectively manages the dispersion on a fibre to ensure that it does not reach unmanageable levels. Management of dispersion becomes critical with increased network capacity, data rate and transmission distance.
Mark Barratt detailed the reasons that dispersion affects the performance of these optical networks: "With 2.5 Gbit/s systems, the time lapse between optical pulses is such that dispersion is not an issue. When you get to 10 Gbit/s systems, dispersion becomes an issue in long-haul networks. With 40 Gbit/s systems, any transmission path of over 10 km must include chromatic dispersion management. Fundamentally, as the space between pulses becomes less, tolerance to dispersion in the network is reduced."
Dispersion slope
A further complicating factor in the control of chromatic dispersion is that dispersion varies across DWDM channels. This variation is referred to as the 'dispersion slope'. In the low, C-band channels, dispersion is significantly different to that in the high band channels.
To date, as noted earlier, dispersion management has been achieved by the use of dispersion-compensating fibre that controls dispersion well for one or two channels, but not along the entire operating band because of dispersion slope. This shortcoming results in much of the bandwidth capacity of the fibre, at the edges of the band, remaining unused. With the packing of more channels onto each fibre, the full bandwidth of the fibre is required.
LaserComm utilises high-order mode technology to precisely manage the dispersion slope of a fibre for all channels simultaneously. The system will work on transmission fibre from any manufacturer. This dispersion management system allows an almost unlimited number of channels to be packed into the operating band.
Critical design factors
There are a number of factors in an optical network that must be considered when designing components. One critical factor is insertion loss. LaserComm's system consists of only three main components, and thus realises very low loss rates. Mr Barratt noted that this is far lower than is achieved with dispersion-compensating fibre.
A further factor is the power of the signal that a particular type of fibre is able to accommodate - fibre performance is limited by the non-linearity effect, which ensues when energy input to the fibre reaches a critical point. The limit for a specific type of fibre is related to the fibre's effective area, calculated in square microns. Single mode fibre has an effective area of approximately 80 square microns; dispersion-compensating fibre achieves 15 square microns. LaserComm's high-order mode fibre attains an effective area of approximately 77 square microns. This results in LaserComm's device being able to handle higher power levels than traditional dispersion-compensation modules.
Commenting on this aspect of LaserComm's device, Mr Barratt said, "The high power tolerance of our device maintains a clear optical signal without stimulating non-linearities, therefore enabling longer transmission distances and the design and integration of other advanced optical components."
High-order mode breakthrough
The key innovation in LaserComm's device is conversion from fundamental signal mode to a selected high-order mode. The properties of the high-order mode fibre are different to those of fundamental mode fibre - allowing manipulation of the signal. By passing the signal through a short section of specially engineered high-order mode fibre, LaserComm's product achieves very high negative dispersion.
"The breakthrough has been in our ability to transform from the single mode to a selected high-order mode, stabilise it and utilise the properties of that mode. One problem that can be addressed through this technique is chromatic dispersion."
Hi-mode DMD product
LaserComm's Hi-mode DMD product is described as a passive device consisting of three main components: two transformers, each at either end of a length of high-order mode fibre. A third-party manufacturer produces LaserComm's specialty high-order mode fibre according to LaserComm's design specification.
The device is connected to transmission fibre and may be positioned at a number of locations in the network. To pre-condition signals, dispersion is managed before amplification - in which case the device will be sited with the optical amplifiers. It can also be sited at the receiver end of the fibre and with EDFAs along the fibre.
A signal entering the device in fundamental mode will hit the transformer and be converted to high-order mode. The signal next passes along a short section of high-order mode fibre where dispersion is reversed and the dispersion slope managed. The signal then goes through a second transformer, which converts it back to fundamental mode and sends it on to the transmission fibre.
Low cost
Discussing the positioning of LaserComm's product, Mr Barratt stated that in the optical space the issue currently is one of achieving higher data rates at lower cost, "Basically the issue comes down to megabits of data per kilometre per dollar."
LaserComm's system addresses each of these issues: the number of channels that may be put over a DWDM system; the bit-rate realised over each channel; and the reach of the signal. The last of these factors, in particular, affects the cost of the network.
According to Mr Barratt, "The single most expensive factor in a DWDM system is converting the signal between the optical and electrical domains. We address the issue of chromatic dispersion and reduce the need for optical-electrical-optical regeneration, thus enabling systems developers to progress in each of the areas cited."
Reliability
LaserComm's device has completed an intensive testing programme, and recently achieved Telcordia qualification for GR-1221, GR-63 and GR-2854 requirements: "The device has been through extensive testing for reliability, in order for us to gain commercial acceptance. This device has to be extremely stable and reliable."
Intellectual property
LaserComm has filed twenty patents relating to the device, covering aspects such as the special fibre and the transformer. Four of these patents have so far been granted.
Market opportunities
LaserComm's market is primarily in long-haul and extended long-haul (1000 km plus) and high-capacity networks. However, 10 Gbit/s networks reaching in excess of 200 km require careful management of chromatic dispersion, and within 40 Gbit/s networks such management is essential over distances of more than 10 km. Therefore, the company's future market will encompass all optical networks, ranging from metro to extended long-haul.
Regarding 40 Gbit/s systems, Mark Barratt stated that LaserComm is currently "Engaged in numerous trials with system developers." He further stated, "LaserComm is either engaged in or has already completed testing with every major system vendor in the DWDM space. We have also conducted testing with many of the new 'innovator' companies."
Alternative solution
In networks up to 500 km, systems vendors currently employ dispersion-compensating modules to combat chromatic dispersion. With the move to longer reach networks, vendors are seeking an alternative solution. Up until now, available options have been either the use of dispersion-compensating fibre - with an associated loss of channels and thus capacity - or the use of sub-banding. The latter solution employs multiple dispersion-compensating modules, each one managing small sections of the operating band, typically four to eight channels. With this solution, traffic must be multiplexed and de-multiplexed down to the sub-bands, making this an expensive and complicated option.
Mark Barratt stated that LaserComm's solution represents a huge saving, particularly when compared to sub-banding. He said, "We can supply a single broadband box to enable precise chromatic dispersion management on a network. On a cost per channel basis, LaserComm's device offers significant cost savings when compared to any other currently available solution."
Market size
CIBC World Markets has calculated the market for chromatic dispersion management in 2001 to stand at $360 million, projected to reach $1.5 billion by 2005. Commenting on these figures, Mark Barratt noted, "Currently the market size for this segment is relatively simple to calculate. The primary technology is dispersion-compensating fibre, with only a handful of players - predominately Lucent and Corning."
Market share
LaserComm expects to take market share from conventional dispersion-compensation fibre suppliers. In addition, the company believes it will facilitate a move to 40 Gbit/s networks where LaserComm's device will improve the economics. As LaserComm is working with DWDM systems developers worldwide, no geographical boundaries to its addressable market are perceived.
Customers and applications
The Hi-mode DMD product is in manufacture and has been sold to a number of system vendors, including companies outside of the U.S., but Mr Barratt was not aware of any units installed on commercial networks. Details of customers could not be disclosed, although it was noted that the list included established players, and the one customer that has been publicly announced, PhotonEx.
In addition to DWDM system suppliers and the 40 Gbit/s optical transmission equipment vendors, LaserComm also works with carriers.
"We have worked with AT&T and a number of other carriers. The carriers have shown a great deal of interest in the capabilities that we can offer them. Having said that, an innovation has to offer significant advantages over current market offerings for the potential customers to show a serious interest. Maybe it has to sound to good to be true."
NTT
It was noted that NTT in Japan has experienced problems operating DWDM systems over dispersion-shifted fibre networks and LaserComm is working with NTT to address this issue. Mark Barratt explained that in the L-band, dispersion-shifted fibre supports DWDM. For this reason carriers such as NTT have been awaiting the availability of DWDM systems that operate in the L-band. As with the C-band, these systems require dispersion management and LaserComm offers a solution for use in both bands. This capability has aroused significant interest in the dispersion-shifted fibre version of the company's device since a number of U.S. carriers have installed dispersion-shifted fibre networks, and therefore face problems similar to those of NTT.
Risks
A scenario posed to Mr Barratt is that carriers have already installed their networks and may see no immediate necessity for upgrades or expansion, particularly given the prevailing market environment. Mr Barratt countered that there is clear evidence that this is not the case. On the contrary, the fact that a carrier has installed the core network means that it can now choose on what to spend its budget. Carriers will look to invest in the best new systems and technologies available.
"The 'best' will equate to systems that enable the carrier to transmit a megabit of data at the lowest cost over their fibre. DWDM system developers are now focusing on advanced systems to give longer network reach, more channels, and higher bit rates. All of these features require improved dispersion management."
Industry alliances
LaserComm is actively pursuing alliance and partnership deals, particularly with suppliers of EDFA and pump components. The company is presently working with both research and development teams of system vendors and with independent component suppliers. These companies are able to utilise the unique capabilities that LaserComm's device offers, particularly the low-loss and high power handling features of the device.
Commenting on this, Mark Barratt said, "We are enabling companies to advance the design of their products, by removing some of the technological limitations that have been restricting them."
Competition
LaserComm believes it holds a unique position in the market and Mark Barratt considers that there are currently no other start-up companies working in the broadband dispersion management field.
"This fact may seem surprising, but it is only through a significant technology breakthrough that we have been able to develop our solution and solve this problem."
The closest competition is seen as arising from incumbents and start-up companies working in the narrow-band dispersion management space, utilising fibre Bragg gratings.
"Fibre Bragg gratings are being developed for narrow-band applications, and look like becoming a viable solution. These can be used for extremely precise dispersion control across a limited number of channels - the primary application would be on ultra long-haul 40 Gbit/s systems."
Future funding
LaserComm is privately funded and considers that within the present economic climate there are limited options to raise additional funding. Mr Barratt stated that until very recently LaserComm was not in a position to raise funding through an IPO due to a lack of commercial products. When such an option would have been feasible, prior to the market downturn, products were in the very early development stage. However, in his view there is still private funding available for good, strong companies.
"Venture capital companies are simply being far more discriminating now over who they invest in than they were during the boom times. Occasionally there may be companies who are unjustly damaged by market conditions. Generally, those with a good business plan, a clear differentiator, and the ability to operate efficiently, will gain financial backing and succeed. I believe strongly that LaserComm is one such company."
OpticalKeyhole.com and the Optical Networks Daily newsletter conduct interviews on the basis of readership interest only. They are not paid for by the participating companies, nor is there any swap for newsletter subscriptions or advertising.
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