Abstract: An avalanche photodiode includes a GeOI substrate; an I—Ge absorption layer configured to absorb an optical signal and generate a photo-generated carrier; a first p-type SiGe layer, a second p-type SiGe layer, a first SiGe layer, and a second SiGe layer, where a Si content in any one of the SiGe layers is less than or equal to 20%; a first SiO2 oxidation layer and a second SiO2 oxidation layer; a first taper type silicon Si waveguide layer and a second taper type silicon Si waveguide layer; a heavily-doped n-type silicon Si multiplication layer; and anode electrodes and a cathode electrode.

Abstract: An avalanche photodiode includes a GeOI substrate; an I—Ge absorption layer configured to absorb an optical signal and generate a photo-generated carrier; a first p-type SiGe layer, a second p-type SiGe layer, a first SiGe layer, and a second SiGe layer, where a Si content in any one of the SiGe layers is less than or equal to 20%; a first SiO2 oxidation layer and a second SiO2 oxidation layer; a first taper type silicon Si waveguide layer and a second taper type silicon Si waveguide layer; a heavily-doped n-type silicon Si multiplication layer; and anode electrodes and a cathode electrode.

Abstract: A method for testing an optical fiber includes: receiving a test optical signal from an optical fiber network, and converting the test optical signal into a test current signal; receiving, by a transimpedance amplifier, the test current signal by using a first working mode and outputting a first test voltage signal; acquiring a swing of the first test voltage signal, and determining whether the swing of the first test voltage signal meets a preset condition; and receiving, by the transimpedance amplifier, the test current signal by using a second working mode and outputting a second test voltage signal when the swing of the first test voltage signal meets the preset condition, where an upper limit and a lower limit of a receiver dynamic range when the transimpedance amplifier works in the first working mode are different from those when the transimpedance amplifier works in the second working mode.

Abstract: Embodiments of the present disclosure disclose an OTDR test signal modulation circuit, including a laser diode drive, a laser diode, a current adjusting unit, and an OTDR control unit. The laser diode drive is connected to the laser diode and is configured to drive, according to an input data signal, the laser diode to transmit data light. The current adjusting unit is connected to the laser diode and the OTDR control unit and is configured to adjust a current flowing through the laser diode according to an OTDR test signal provided by the OTDR control unit, so as to modulate the OTDR test signal to the data light transmitted by the laser diode. Moreover, the embodiments of the present disclosure also disclose a passive optical network system and apparatus.

Abstract: A method for testing an optical fiber includes: receiving a test optical signal from an optical fiber network, and converting the test optical signal into a test current signal; receiving, by a transimpedance amplifier, the test current signal by using a first working mode and outputting a first test voltage signal; acquiring a swing of the first test voltage signal, and determining whether the swing of the first test voltage signal meets a preset condition; and receiving, by the transimpedance amplifier, the test current signal by using a second working mode and outputting a second test voltage signal when the swing of the first test voltage signal meets the preset condition, where an upper limit and a lower limit of a receiver dynamic range when the transimpedance amplifier works in the first working mode are different from those when the transimpedance amplifier works in the second working mode.