Claims
- 1. A circuit for receiving pulse width modulated data signals in an optical fiber communications system comprising:
- means for amplifying a pulse width modulated signal;
- means for comparing the amplified pulse width modulated signal with a reference quantity and
- means connected to said pulse amplifying means for limiting the peak value of the amplified pulse width modulated signal, said limiting means including means connected to an output of said comparing means for adjusting the duty cycle of the amplified pulse width modulated signal.
- 2. The circuit of claim 1, wherein said means for adjusting the duty cycle comprise a one shot module and said means for limiting further comprises;
- a charge pump amplifier having an input connected to an output of said means for comparing; and
- a limiting automatic gain control integrator having an input connected to said means for comparing and an output connected to said means for amplifying.
- 3. The circuit of claim 2, wherein said means for limiting further comprises:
- a peak buffer amplifier having an input connected to an output of said charge pump amplifier, an output connected to an input of said limiting automatic gain control integrator, and an output connected to an input of said means for comapring.
- 4. The circuit of claim 3, wherein said means for amplifying comprise:
- a transimpedance amplifier which converts a single pulse width modulated signal to a dual output signal in which the dual outputs are essentially equal in amplitude, but 180 degrees out of phase;
- a plurality of amplifiers connected in series with each other and with the dual outputs of said transimpedance amplifier; and
- an interstage low pass filter connected in series with said plurality of amplifiers.
- 5. The circuit of claim 3, wherein said means for limiting further comprise a leakage isolation diode whose cathode is connected to an output of said charge pump amplifier and whose anode is connected to an input of said peak buffer amplifier, and a peak signal holding capacitor connected to the anode of said leakage isolation diode.
- 6. The circuit of claim 4, wherein said means for limiting further comprise a leakage isolation diode whose cathode is connected to an output of said charge pump amplifier and whose anode is connected to an input of said peak buffer amplifier, and a peak signal holding capacitor connected to the anode of said leakage isolation diode.
- 7. The circuit of claim 1, wherein said means for amplifying comprises:
- a transimpedance amplifier which converts a single pulse width modulated signal to a dual output signal in which the dual outputs are essentially equal in amplitude, but 180 degrees out of phase;
- a plurality of amplifiers connected in series with each other and with the dual outputs of said transimpedance amplifier; and
- an interstage low pass filter connected in series with said plurality of amplifiers.
- 8. The circuit of claim 1 wherein said means for limiting further comprise automatic gain control means including means for adjusting the gain of the automatic gain control means to restrict the peak voltage to be substantially equal to a reference voltage.
- 9. The circuit of claim 1 wherein said means for adjusting the duty cycle include means for adjusting the duty cycle of a received pulse in accordance with the time elapsed since a previous received pulse.
Parent Case Info
This application is copending with U.S. applications Ser. No. 740,149 and 740,150, both filed June 3, 1985. U.S. application Ser. No. 740,149 claims the clock symmetry restoration circuit described in this application and U.S. application Ser. No. 740,150 claims the optical fiber communications system described in this application.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
3176238 |
Dickerson, Jr. |
Mar 1965 |
|
4027152 |
Brown et al. |
May 1977 |
|
4581731 |
Tomikashi et al. |
Apr 1986 |
|
Non-Patent Literature Citations (1)
Entry |
O'Neill, "Fiber Optic Receiver"-EDN, Jun. 20, 1979, vol. 24, #12, p. 158. |