Optical transmitter
AssigneeNEC Corporation
InventorIppei Kobayashi
Life of this patent
Estimating the term…
Abstract
An optical transmitter having an automatic output controlling function converts monitor current of a laser into a voltage and detects an average value of the voltage. The average value is compared with a mark-space ratio outputted from a mark-space ratio detection circuit by a bias control circuit, by which a bias circuit is controlled. Meanwhile, the average value described above is divided by the mark-space ratio from the mark-space ratio detection circuit by an operation circuit, and a resulting value is compared with a reference voltage (Vref) and amplified by a pulse current controller. The pulse current driver is controlled with the amplified output of the pulse current controller. Finally, outputs of the pulse current driver and the bias circuit are added to drive the laser.
Claims6
An optical transmitter, comprising:
- a laser for converting an electric signal into an optical signal;
- a pulse current driver for receiving an input signal and driving said laser according to a control signal inputted thereto separately;
- a bias circuit for cooperating with said pulse current driver to drive said laser in order to provide a bias for keeping an optical output level of said laser at a predetermined value;
- a mark-space ratio detector for detecting a mark-space ratio of the input signal;
- a photodiode for detecting back light of said laser and outputting monitor current of the optical signal;
- a current/voltage converter for converting the monitor current from said photodiode into a voltage;
- an average value detector for outputting an average value of the output of said current/voltage converter;
- a bias controller for comparing the average value with the mark-space ratio, amplifying a difference between the average value and the mark ratio and outputting a signal for controlling said bias circuit;
- an operation circuit for receiving the average value and the mark-space ratio and performing a predetermined operation;
- and
- a pulse current controller for comparing a result of the operation of said operation circuit with a fixed reference voltage, amplifying a difference obtained by the comparison and outputting the amplified difference as the control signal for said pulse current driver.
Dependencies are inferred from the claim text.