intended to limit the scope of the invention described in this application a gallium doped silica preform doped with thulium was fabricated using mcvd an all vapor process was used where gallium chloride and rare earth chelate were transported to the mcvd reaction zone via a heated injection assembly the mcvd chelate injection tube assembly used is similar to that outlined in the article by tumminelli r p et al u201c fabrication of high concentration rare earth doped opticalfibers using chelates u201d j lightwave tech vol 8 no 11 1990 p 1680 sicl 4 bubbler t 25 u00b0 c 20 sccm standard cubic centimeter per minute 5 grams of gacl 3 was loaded into a quartz bubbler and heated to 180 u00b0 c about 10 g of tm chelate was dispersed in sio 2 sand loaded into a quartz bubbler and heated to 170 u00b0 c these were connected to the heated injection tube assembly a 16 mm u00d7 20 mm substrate tube was used for the mcvd process the gallosilicate core was deposited in the following manner the 20 sccm of sicl 4 was sent to the mcvd reaction zone the gacl 3 t 180 u00b0 c was then sent to the reaction zone when a stable reaction zone was established the tm chelate then introduced to the mcvd reaction zone a relatively small flow rate for the tm was used to dope a low concentration of rare earth into the glass this was to minimize any ion u2014 ion interactions that could complicate subsequent spectroscopy two passes were deposited under these initial conditions for the third core deposition pass the temperature for the gacl 3 bubbler was increased to 210 u00b0 c after three core pass.