Originally deployed for 1-Gbit Ethernet, a lot of existing
fiber-optic cable could manage 10 Gbits/s, thanks to
IEEE 802.3aq 10GBase-LRM (long-reach multimode).
This standard was approved in 2006 to address multimode
dispersion in legacy fiber with a technology called electronic
dispersion compensation (EDC).
Previous chip sets have depended on amplifiers that were
less than optimal for the new standard. But Inphy’s 1348TA
S03D transimpedance amplifier
(TIA) with automatic gain control
(AGC) exceeds the 802.3aq
requirements. Its performance
resembles the company’s earlier
1348TA S01D, which supports
up to 11.3 Gbits/s and
amplifies input currents
between 20 µA and 2.5 mA p-p
with less than 5% harmonic distortion.
Typical input sensitivity is
–18 dBm with a bit error rate
(BER) of 10 to 12. In AGC
mode, gain is set internally
through a peak detector. Gain
also can be controlled externally.
An integrated feedback circuit
controls the dc offset to
maintain 50% eye crossing, or
else the eye crossing can be externally adjusted. Small-signal
bandwidth is greater than 8 GHz, with an output return loss
greater than 8 dB, up to 12 GHz.
The new amp meets and exceeds the 802.3aq requirements
with higher gain, an extended power-supply operating
range, and output electrostatic discharge (ESD) protection to
more than 1 kV (Human Body Model). As a result, the 1348TA
S03D meets 10G SFP+ (small form-factor pluggable) requirements
from –11 dBm (optical
modulation amplitude, or OMA)
to 3 dBm (OMA) without an
additional buffer amp.
According to Inphy, the integrated
TIA/AGC has passed
stringent testing to ensure complete
interoperability with all
leading EDC chips in the market
(see the figure). Specific details
about testing are available from
the company.
The Inphy 1348TA is available
in engineering samples,
with volume shipments expected
to begin in the first quarter
of 2008.
Inphy
www.inphy-corp.com
