Dendrobium violaceum
Kraenzl. in H.G.A.Engler (ed.), Pflanzenr., IV, 50 II B 21: 108 (1910).

From my favorite section, Oxyglossum.

This species is found in New Guinea's montane forests, 700-2000m. The flowers are 3cm wide. Plant size 15-20cm. I/C grower.