Based on the graded-index p rofile ofwaveguides fabricated byAg+ 2Na + ion exchange, the p rincip le ofmul-timode interference (MM I) optical splitter is studied. A buried 1 ×8 MM I op tical splitter is designed and fabricated on K9 glass substrate. Testing investigations show that this compact splitter has an excellent uniformity of 0. 5dB and easy to manufacture via loose tolerances.