High-speed data modems dominate Western Cable Show
High-speed data modems dominate Western Cable Show
At the Western Cable Show held last December in Anaheim, CA, cable-TV operators took a giant leap toward providing data services over high-speed data modems at rates 1000 times faster than today`s standard telephone modems.
Taking part in the conference were all the major cable-TV multiple system operators, including Tele-Communications Inc., or TCI, Time Warner Cable, Comcast Corp., Cox Cable Communications and Continental Cablevision. In a milestone agreement, these companies plan to standardize on all cable-TV modem equipment that they purchase. The first three companies, for example, plan to buy as many as 350,000 cable modems from Motorola in Arlington Heights, IL. Many cable-modem types are available, but none are inexpensive or interoperable.
This cable-modem development is expected to impact fiber-optics-based communications because only 10% of cabling plants are capable of carrying data from the home to the headend. Other plants will have to deploy more fiber to achieve two-way service.
More than 20,000 attendees jammed the Anaheim Convention Center to see the latest cable-TV technology. This show has generally been one of the largest U.S. shows for cable-TV engineers because it occurs when many companies are planning their budgets for the following year. But this year, a significant number of attendees represented telephone and data communications companies.
Other major moves coming out of the Western Cable Show dealt with cable-TV organizations embracing modem standards. First, AT&T Network Systems, Hewlett-Packard Co., Hybrid Networks and Intel Corp. agreed to work together to create interoperable first-generation modems. In addition, a large group of vendors and multiple system operators agreed to work through Cablelabs to establish standards for data networking.
Standardizing on equipment
Underscoring the significance of standardization, John Malone, chief executive of TCI, said, "There needs to be standardization to make sure cable modems are inexpensive. In the next generation of cable modems, we are looking for more cable commonality so that vendors may enjoy mass-market sales, and cable customers can be assured that their devices work on all cable systems."
The mass deployment of cable modems will probably precede the digital set-top boxes that were highly touted last year as the next technological advancement. For example, despite significant orders last year from TCI and Time Warner for digital set-top boxes, none of them have shipped. Malone suggested that the protocols being developed for high-speed data services will also be adopted for digital interactive television.
Cable TV has traditionally been used as a broadcast architecture in which a single laser transmits over as many fibers as possible. As cable operators look at rolling out new services such as high-speed data or video-on-demand, they need a way to send a different signal to each neighborhood. One approach is to put a separate laser onto each fiber, but that tends to be more expensive than splitting the laser output into multiple fibers.
An example of narrowcasting, or the transmission of large amounts of information to select groups of subscribers, comes from Fiber Optic Network Solutions Corp. in Northborough, MA. Its Fonsmitter laser transmitter can send a different signal to each node on a cable-TV plant by using a 1319-nanometer laser (see page 1). This signal can be split 32 times into different fibers, and each of these signals can be externally modulated. The output power from each modulator is 2.5 and 20 microwatts where the signal is split into 32 and four fibers, respectively.
According to Mike Noonan, president of Fiber Optic Network Solutions, "Cable-TV providers have been begging for affordable narrowcasting and redundancy capabilities. Our [laser transmitter] provides the cable-TV and telephone industry with a solution for meeting consumer demand for services such as a personal World Wide Web site, video-on-demand, voice capability and interactive services. The increase in output capabilities enables more reliable services, attracts more subscribers, increases revenues and decreases costs."
Another company, ADC Video Systems, based in Meriden, CT, introduced a similar architecture for narrowcasting based on its Homeworx hybrid fiber/coaxial-cable distribution system. ADC`s platform is a scalable system that allows a cable operator to deploy a broadcast architecture and can be upgraded to support narrowcasting. Initially, a cable operator could use one 40-microwatt 1550-nm laser and modulator to send a signal into multiple fibers. When cable operators need more bandwidth for a neighborhood, they can replace the single modulator with two or more, without having to add any lasers. This system is expected to go into testing in February and into full production in the second quarter of 1996.
According to John Holobinko, vice president of marketing and strategic planning for ADC Video Systems, "Homeworx was designed to build networks with scalability, so operators can better time network capital costs with additional services and their accompanying revenue. Network operators can now systematically and economically control their expansion. This gives hybrid fiber/coaxial-cable systems a significant leg up on switched digital video network designs, which are far more capital-intensive up front before rollout of revenue-producing services."
The System 70 fiber-optic distribution platform of Scientific-Atlanta in Norcross, GA, provides a different approach for narrowcasting. This system supports low-cost, low-power lasers and enables each laser to transmit on only one fiber. The transmitter has two radio-frequency input jacks so that cable operators could have a common signal in the 50- to 550-megahert¥range and a special signal for each neighborhood in the 550- to 750-MH¥band for narrowcast services.
The System 70 chassis can hold 10 lasers compared to only four in its predecessor System 60 chassis. Robert Colmus, manager of product marketing for distribution and fiber products at the company, says that improved circuitry allows the use of a lesser-grade laser to obtain the same optical link budget. System 70 began shipping in December.
Scientific-Atlanta also introduced the Model 6910 fiber-optic receiver, which is a low-cost receiver and radio-frequency amplifier for distributing signals onto the coaxial-cabling plant. The cost has been reduced so that the receiver can be deployed to a small number of homes in passive or fiber-rich networks.
Cable operators at the Western Cable Show also discussed long-distance fiber-optic systems used to transmit video. These systems are becoming attractive as cable operators continue to link large fiber-optic metropolitan area networks.
Illustrating these video-transmission products at the conference, Harmonic Lightwaves Inc. in Santa Clara, CA, demonstrated its Maxlink 1550-nm fiber-optic transmission system. The unit can send 80 video channels down a 100-kilometer link while maintaining a carrier-to-noise ratio of 53 decibels. This plug-in module for Harmonic`s HL4000 transmitter platform uses an erbium-doped fiber amplifier to boost the output power to 17 dB in each fiber. Although other fiber amplifiers are able to achieve higher output powers, they suffer from stimulated Brillouin scattering when working with a single fiber; Brillouin scattering reduces the power going down the fiber.
Many next-generation services, including telephony and high-speed data, are beyond the capabilities of individual companies, so companies are establishing joint ventures to serve the cable-TV industry. At the conference, Northern Telecom Ltd. and Antec Corp. established two joint ventures to serve the cable-telephony market. The first joint venture, Integration Technologies Inc., will serve as a consulting partnership that will be based near Denver. The second, based in Atlanta, aims at distributing Northern Telecom`s Cornerstone voice and data hybrid fiber/coaxial-cable distribution system and other products agreed upon. q
George Lawton writes from Brisbane, CA.