Also, if Im right:
you need a change in logic level to send to your PIC if i.e. the LVPECL output is no more high=2.4V, also went/changed to "0=1.6V?
Wher is comparing reference voltage level pls of you PIC, or is it a TTL compatible Input?
How much Volts is it?
Usual s if a ECL IC supplyd with +3V3 or 5V than=PECL!
A comparing logic level(Vbb) is at max ca. +1.9V (Vcc-Vbb, 3V3-1V35), if you hase PECL in system; is it supplyed (as lvpecl per definition is) with +3v3 or not?
Also, what you need is no more as a comparator at +Vbb referenced, in concret case between 1355 & 2075mV, practically to middle, as the attachement tells you too.
Compare pls for +1.75V and is your circuit in extrems functioning too, but you need a good Uref!
Other possibilty is onlya SO8 IC (NB100ELT23L)
as Level Converter to apply and works up to 160MHz, see attachement...
K.