Background Report1394b:Optoelectronic Data

Communications

ECE 4006C

Tiffany Lovett

Tornya Moore

Mareisha Winters

January 31, 2002

Key features of 1394?

• It is a hardware and software standard for transporting data at 100, 200, or 400 Mbps

• It is a digital interface - no need to convert digital data into analog

• It is physically small and can replace larger, more expensive interfaces

• It is easy to use

Key features of 1394?

• It is hot pluggable - users can add or remove 1394 devices while the bus is active

• It is inexpensive

• It is a scaleable architecture - can mix 100, 200, and 400 Mbps devices on a bus

• It has a flexible topology

• It is non-proprietary - there is no licensing problem to use for products.

1394 Cable

• Is a small, thin serial cable

• Contains six wires: two of the wires carry power; the remaining four wires are grouped into two twisted signal pairs

How 1394 Works

• Supports both asynchronous and isochronous data transfers

• 1394 device requests control of the physical layer

• Asynchronous: The address if the sender & receiver is transmitted by the packet data. Once the receiver accepts the packet, an acknowledgement is returned to the original sender

• Isochronous: The sender requests an isochronous channel with a specific bandwidth. Isochronous channel IDs are transmitted followed by the packet data. The receiver monitors the incoming data’s channel ID

Why 1394b?

• 1394b is a revision of the initial 1394 standard

• 1394b is twice the speed, and allows for longer distances

• It provides new connection options such as Plastic Optical Fiber, Glass Optical Fiber and UTP-S. Previously 1394 could only be connected via copper cabling

• 1394b is a prime choice for connecting personal computers with digital devices (i.e. cameras, DVD players, and camcorders)

Photodetectors

• Optoelectronic device that senses and measures the output of a typical light source

• There are three steps in the photodetection process:

(1) absorption of optical energy and generation of carriers

(2) transportation of the photogenerated carriers across the

absorption region

(3) carrier collection and generation of a photocurrent• The three main types are photoconductors, PIN photodiode, and

Avalanche photodiodes

• For high-speed applications the PIN photodiode is the best choice because it has no internal gain and can attain very large bandwidths.

Emitters

• Three types are LEDs, Edge emitting lasers, and VSCELs

• LEDs produce light by a process known as spontaneous emission, resulting in incoherent light

• Lasers produce light by stimulated emission, which results in coherent light

• For high-speed applications VCSELs are superior to LEDs and Edge emitting lasers because they achieve high data rates easier and they are less expensive

Project Goals

• Investigate and purchase of PIN photodiodes and VSCELs available that meet the 1394b specifications

• Implement optoelectronic portion of the 1394b test bed with evaluation boards

• Verify functionality of PIN photodiodes and VSCELs as receivers and transmitters for 1394b

• Implement own version of 1394b test bed and verify functionality