Company preps holographic storage for commercial deployment
LONGMONT, COLO.
(click thumbnail)Maxell's Tapestry disks will cost approximately $100-$125 per 300 GB disk.
If you tried to house all the people who live and work in downtown New York City in single story buildings, you wouldn't have room. That's why they built high-rises on Manhattan Island.
Keep that same concept in mind and you'll understand holographic storage's advantage over other optical-based storage technology.
Holographic storage writes into the entire depth of its disk media, allowing hundreds of times the same amount of data to be stored on the same sized disk. It also enables much faster data transfer rates.
InPhase Technologies of Longmont, Colo., has brought holographic storage technology into the broadcast arena, and will begin delivering 300 GB removable disks and decks around the end of the year. Their first station customer can't wait.
"We are chomping at the bit, as it were, to get involved with implementing this technology," said James Ocon, deputy director of engineering for Pappas Telecasting. "I look at this technology as kind of the 'Holy Grail'... it will change on a daily basis how we access information and how we will manage data."
The first generations of InPhase's holographic storage technology disks will be WORM, write once, read many, like the original CDs and DVDs. They expect to deliver 800 GB WORM disks in 2008 and 1.6 TB WORM disks in 2010, all backward-compatible with the 300 GB disks. The company is also working on rewritable holographic disks.
Pappas will be using the holographic storage in its all HD facility, now under construction, in Reno. "We're trying to take two stations (KAZR-TV/KREN-TV) and put them in under 10,000 sq. ft., inside a shopping mall," said Ocon.
"Not only do we have our video assets that we want to archive, but we have obviously all the usual paperwork contracts from logs and rundowns and everything else, and we want to go tapeless because of the physical ergonomic type of requirements we have due to space."
The amount of video that can be stored on a 300 GB holographic disk varies with the video format (see chart), but it's considerably more than current optical media. InPhase points to the laws of physics putting a barrier to increasing storage on the surface of other media.
"Both magnetic and optical traditional are focused on making the surface features as small as possible, and optical with Blu-ray has kind of gone as far as they can go in that regard," said Kevin Curtis, chief technology offiicer at InPhase. At $100-125 per 300 GB disk, holographic storage competes effectively with tape, and InPhase points to the effectively limitless shelf life and durability of data written to their disks. Because the first disks are WORM, InPhase is targeting archiving as its market.
The disks themselves contain a photopolymer sandwiched between two very flat, clear pieces of polycarbonate, sheathed in a cartridge. "If you closed your eyes and held them, you'd think it was an MO disk," said Rich D'Ambrise, director of technical marketing at Maxell, the manufacturer of the holographic disks, which have been named "Tapestry."
D'Ambrise described the photographic nature of the holographic writing process: "Basically what we do when we write to it with the laser we're exposing the photopolymer to light, similar to what a camera does when it opens the shutter, exposing the film to light."
Holographic disks also don't spin at thousands of rpm like other disk media. "It does turn, ever so slowly, almost like a second hand on a watch, to access a different portion of the disk," said D'Ambrise.
"The transfer rate on the first-gen product is 160 Mbps, and as far as on the drive for the first-gen, we're looking at 250 milliseconds average seek time," he said. "The media itself does have a two to three year shelf life before it is used, and once it's exposed to light, there's no problem as far as deterioration of the media."
HOW IT WORKS
So how does holographic storage write into the depth of the media?
First, rather than write as an individual bit on the media, InPhase gangs together around 1.4 million bits at a time into what it calls a "page."
The page is written into the photopolymer layer of the disk using a pair of laser beams, the data beam and the reference beam. (Technically, they're split from the same original beam.)
A device called the spatial light modulator (SLM) encodes the data, along with error correction and channel codes, onto the data beam. That modulated data beam is applied perpendicular to the disk at a chosen location.
The reference beam determines where, and at what angle in the photopolymer layer, the data from the modulated beam will be written. Though the metaphor isn't precisely correct, the reference beam can be thought of as the elevator buttons that determine which floor to stop at in our high-rise storage media.
The reference beam is aimed into the disk at an angle to intersect, or interfere with the modulated beam at a precise depth and angle. "That interference pattern between those two beams forms a light/dark pattern that exists throughout the entire thickness," Curtis said.
"That's what the media records, that light/dark pattern by changing the optical density of the media throughout the volume. To read it out, you put in the same reference beam you put in to store that page." That light/dark pattern projects through the bottom of the disk where it is read by a detector, basically a CMOS sensor.
Groups of pages that are stored in the same volume, 128 in all in the first generation product, are called a "book." "You can change the angle of incidence on the reference beam a bit and story another page in the exact same volume," said Curtis. "That's called angle multiplexing."
InPhase will be delivering the drives as both standalone and, through third party manufacturers, as auto-loaders or jukeboxes. "Part of the reason we picked the MO form-factor for the cartridges is so you can use robotics," said Curtis.
Because of the demands of hi-definition material, and thus the need for many times the storage space as needed for SD, other companies have turned to holographic storage, including Turner Entertainment, which boasts a library of more than 200,000 movies along with 25,000 commercials and 49,000 promotional spots, now stored on digital tape.
Pappas' Ocon puts the coming of holographic storage succinctly: "The timing couldn't be any better."
