InGaAsP l.e.d.s emitting at 1.24 μm are fabricated. Their characteristics at 100 mA are as follows: output power coupled into the fibre of 77 μW, a spectral halfwidth of 0.1 μm and a cutoff frequency of 70 MHz. The cutoff frequencies are proportional to the square root of the bias current. The recombination coefficient is estimated to be 5 × 10−10cm3/s