We investigate the use of uncooled lasers in an optical fiber transmis
sion system employing quadrature-phase-shift keyed (QPSK) signals on s
ubcarriers. The BER of a 2Mb/s QPSK channel is measured in a system co
ntaining 60 subcarriers. Error-free performance (BER < 10(-9)) is achi
eved over a wide range of modulation depths. This demonstrates that th
ese inexpensive lasers can be used in multi-channel digital systems.