Download Proposed Details for TP2 and TP3 Tests

Questions on Stressed RX Test E-O and E-O-E Linearity
Lew Aronson – Finisar
Abhijit Shanbhag - Scintera
August 24, 2004
Page: 1
Lew Aronson
Question 1 on TP3 Linearity
• With the ISI generator before E-to-O, there will be intramodal dispersion which
will lead to cross-products and non-linear ISI after the PIN (due to square-law,
similar as with chromatic dispersion), which the EDC may not be intended for.
–
Not an issue for TP3 test since there is a very short fiber between source and
DUT (I.e. no significant optical intramodal dispersion in TP3 test)
–
[Believe references exist that E-O-E process turns out to be linear. Cross
products average out.]
Page: 2
Lew Aronson
Question 2 on TP3 Linearity
• With No Fiber, I(t) is the data-modulated output of the ISI generator and h(t) is
the laser filter function (assumed to be perfectly linear), the o/p would be
sqrt(I(t))*h(t)). The PD output is then [(sqrt(I(t))*h(t))]^2. The EDC is designed to
compensate for channel of the form I(t)*(sqr(p(t))), where p(t) is the cumulative
(optical) channel impulse response.
–
Potential Issue with Low Bandwidth or Non-Linear Source
–
Can be Controlled by Signal Characterization Test Portion of Stressed RX Test
Definition.
•
Test Signal for TP3 Stressed RX Test Should be Specified and Measured Optically into
a Linear Reference Receiver (e.g. with isolated one pattern).
•
Mismatch between electrical ISI generator and received ISI can be detected and
corrected by either by using better E-O source or compensation of electrical ISI in
order to achieve the required ISI.
Page: 3
Lew Aronson