IBM Power Systems 775 Manual page 35

Optics physical package
The optics physical package includes the following features:
Individual transmit (Tx) and Receive (Rx) modules that are packaged in Tx+Rx pairs on
glass ceramic substrate.
Up to 28 Tx+Rx pairs per module.
uLGA (Micro-Land Grid Array) at 0.7424 mm pitch interconnects optical modules to
ceramic substrate.
12-fiber optical fiber ribbon on top of each Tx and each Rx module, which is coupled
through Prizm reflecting and spheric-focusing 12-channel connectors.
Copper saddle over each optical module and optical connector for uLGA actuation and
heat spreading.
Heat spreader with springs and thermal interface materials that provide uLGA actuation
and heat removal separately for each optical module.
South (rear) side of each glass ceramic module carries 12 Tx+Rx optical pairs that
support 24 (6+6) fiber LR-links, and 2 Tx+Rx pairs that support 2 (12+12) fiber D-links.
North (front) side of each glass ceramic module carries 14 Tx+Rx optical module pairs
that support 14 (12+12) fiber D-links
Optics electrical interface
The optics electrical interface includes the following features:
12 differential pairs @ 10 GB per second (24 signals) for each TX optics module
12 differential pairs @ 10 GB per second (24 signals) for each RX module
Three wire I2C/TWS (Serial Data & Address, Serial Clock, Interrupt): three signals
Cooling
Cooling includes the following features:
Optics are water-cooled with Hub chip
Cold plate on top of module, which is coupled to optics through heat reader and saddles,
with thermal interface materials at each junction
Recommended temperature range: 20C – 55C at top of optics modules
Optics drive/receive distances
Optics links might be up to 60 meters rack-to-rack (61.5 meters, including inside-drawer
optical fiber ribbons).
Reliability assumed
The following reliability features are assumed:
10 FIT rate per lane.
D-link redundancy. Each (12+12)-fiber D-link runs normally with 10 active lanes and two
spares. Each D-link runs in degraded-Bandwidth mode with as few as eight lanes.
LR-link redundancy: Each (6+6)-fiber D-link runs normally with six active lanes. Each
LR-link (half of a Tx+Rx pair) runs in degraded-bandwidth mode with as few as four lanes
out of six lanes.
Overall redundancy: As many four lanes out of each 12 (two lanes of each six lanes) might
fail without disabling any D-links or LR-links.
Expect to allow one failed lane per 12 lanes in manufacturing.
Bit Error Rate: Worst-case, end-of-life BER is 10^-12. Normal expected BER is 10^-18
Chapter 1. Understanding the IBM Power Systems 775 Cluster
21