Subcarrier systems using uncooled, unisolated lasers

The low cost of uncooled, unisolated lasers makes their use desirable in many applications. Unfortunately, the lack of a temperature controller and optical isolator leads to many impairments, including variations in signal and noise levels, as well as impulse noise. Although these impairments prevent these lasers from displacing the very linear lasers used to transport AM-VSB signals in CATV systems, their performance is adequate for many subcarrier systems where cost prohibits the use of high performance lasers. These systems typically transmit digital signals on RF subcarriers, using modulation formats with lower carrier-to-noise ratio (CNR) requirements than AM-VSB signals