Fsk direct modulation system of semiconductor laser

Abstract

Abstract PURPOSE:To prevent the frequency variation of an LD based on a temperature change by controlling driving currents at modulation input pulses of '1' so that frequency variation under the two high and low states and the intermediate state is equalized. CONSTITUTION:A frequency discriminator circuit 9 frequency-discriminates an output from a PD 8 by predetermined frequency discrimination characteristics, and generates a discrimination output having magnitude corresponding to displacement from center frequency and polarity. A local optical oscillator 7 varies optical oscillation frequency in response to the discrimination output from the frequency discriminator circuit 9, thus keeping the optical oscillation frequency at oscillation frequency f2 at the time of driving currents corresponding to '0' of the input pulses of an LD 3. The output of (f2-f1) is passed through a low-pass filter 10, and the output of f3-f2 is passed through a low-pass filter 11. An output from the low-pass filter 11 is mixed with an output from the low-pass filter 10 in a mixer 13, and the output of the difference frequency of both outputs is acquired. The output is fed back to a coder 5, and controlled so as to adjust the difference of the high and low variation of driving currents corresponding to '1' generated in the coder 5 at zero.

Inventors

• 👤 Chiaki Osawa
• 👤 千晶 大沢
• 👤 Terumi Chikama
• 👤 輝美 近間
• 👤 Masami Goto
• 👤 後藤　正見
• 👤 Kazuo Hironishi
• 👤 広西　一夫

Bibliographic Details