Optical driving device and optical communication system
AssigneeRenesas Electronics Corporation
InventorSeiji Kawata
Life of this patent
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Abstract
An optical driving device and an optical communication system are provided which can improve signal quality of laser light that uses a PAM method. A laser driver drives a semiconductor laser by using an N-level (N is an integer of 3 or more) PAM signal. A clock control circuit determines a driving timing of the laser driver. In a case where N=4, for example, the clock control circuit determines a driving timing in association with a transition of the PAM signal from a fourth level to a first level to be earlier than a driving timing in association with a transition in an opposite direction by a first time, assuming that levels are the first level, . . . , and the fourth level in an order from a level at which light intensity is minimum.
Claims15
An optical driving device that drives a direct modulation type semiconductor laser, comprising:
- a laser driver that drives the semiconductor laser by using an N-level (N is an integer of 3 or more) PAM (Pulse Amplitude Modulation) signal;
- and
- a clock control circuit that determines a driving timing of the laser driver,
- wherein the clock control circuit determines the driving timing in association with a transition from an N-th level to a first level to be earlier than the driving timing in association with a transition from the first level to the N-th level by a first time, assuming that N levels are the first level, a second level, . . . , and the N-th level in an order from a level at which light intensity is minimum.
An optical communication system comprising:
- an optical fiber;
- an optical transmission device that converts digital data to a four-level PAM (Pulse Amplitude Modulation) signal and transmits laser light modulated with the PAM signal to the optical fiber;
- and
- an optical receiving device that receives the laser light from the optical fiber and demodulates the laser light,
- wherein the optical transmission device includes
- a direct modulation type semiconductor laser,
- a laser driver that drives the semiconductor laser by using the PAM signal, and
- a clock control circuit that determines a driving timing of the laser driver, and
- wherein the clock control circuit and determines the driving timing in association with a transition from a fourth level to a first level to be earlier than the driving timing in association with a transition from the first level to the fourth level by a first time, assuming that four levels are the first level, a second level, a third level, and the fourth level in an order from a level at which light intensity is minimum.
Dependencies are inferred from the claim text.