I suppose the Anritsu PG o/p can support 50 Ohm to ground? If your laser driver can take CML inputs, these are very likely pulled up to +Vcc - check the Maxim datasheet. If so, simply a.c couple the Anritsu PG's output via good blocking caps & watch out for the differential skew.
What are good blocking caps for data transmission? The best are from Picosecond Pulse Labs. However you've got some ground to cover before requiring such quality, so I recommend starting with a X7R 10nF 0805 cap that you can solder between two SMA launchers - tab to cap to tab, GND to GND.
If your PG can output only ECL then you can always use a translator IC to get PECL out of the NECL:
http://www.onsemi.com/pub/Collateral/MC10EP90-D.PDFis a 3.0 GHz 3.3V / 5V Triple ECL Input to LVPECL/PECL Output Translator.
You seem to have good equipment, so enough of the sermon - let's see a good eye now!
M.G.Rajan
www.eecalc.com