It is theoretically demonstrated that a succession of four unchirped g
ratings, similar to 20 mm long, induces a negative chromatic dispersio
n in transmission of -100 ps/nm over a 0.2-nm bandwidth, with a power
loss below 1 dB. The stability of the proposed arrangement is also con
sidered and found to be within today's technology. (C) 1996 Optical So
ciety of America