3. Transceiver characteristics
3-1 General characteristics
The principal characteristics of the developed X2
transceiver is shown in Table 2. As a result of decreased
power dissipation at the optical transmitter unit and
optical receiver unit, the total power dissipation of this
transceiver is 3.2 W typical and 3.8W maximum in an operating case temperature range of 0 to 70 deg. C.
The electrical eye diagram of XAUI output after 50
cm transmission over a standard FR-4 PCB, of which relative
dielectric constant is 4.7, is shown in Fig. 12. Even
after transmission over 50 cm on a FR-4 PCB, the XAUI
signal eye diagram satisfies the far-end mask specifications
defined in the IEEE802.3ae 10GbE standard.
As for electro magnetic interference (EMI), the
transceiver complies with the FCC Part 15 Subpart B
Class B requirements in a frequency range up to 40
GHz, having a margin of more than 10 dB even at the
highest EMI frequency of 10.3125 GHz. Figure 13 is a
chart showing the EMI measurement result.
3-2 Optical transmitter characteristics
Figure 14 shows the optical eye diagrams before
and after passing a fourth order Bessel Thomson filter at an ambient temperature of 25 deg. C. The result of
the 10GE eye mask test is also reported in Fig. 14. It
shows wide enough mask margins of 20% or more in a
case temperature range of 0 to 70 deg. C.
3-3 Optical receiver characteristic
Figure 15 shows the receiver sensitivities in nonstressed
and stressed conditions. Both show enough
margins from the IEEE802.3ae 10GBASE-LR specifications.
The figure also indicates that a stable receiver sensitivity
is obtained in stressed condition and very little
degradation is observed compared with the result in
non-stressed condition.
4. Conclusions
The authors have developed a new X2 optical transceiver
that is fully compliant with the IEEE802.3ae
10GBASE-LR specifications. The transceiver shows
excellent optical performance and very low power consumption
as well as conformance to the EMI regulations.
In contrast to the traditional approach that
requires costly parts and assembly techniques to achieve
high performance, the new approach provides high performance
at low cost. This new approach includes the
following new developments;
1) the LD whose high frequency
characteristics and temperature characteristics
are optimized for 10GbE application,
2) the PD that
delivers wide bandwidth at low power supply voltages,
and
3) the coaxial TOSA and ROSA that use inexpensive
TO-Headers. The new X2 transceiver requires low
supply voltage and therefore its power consumption is
the lowest level in the industry. The new structure
applied to the OSA for reducing EMI radiation via optical
receptacles will provide enough margins to the EMI
regulations, even when the X2 modules are installed at
very high density. It is prospected that this new X2 optical
transceiver will contribute to the further spread of
10GbE. |
