Data transmission method, apparatus, and system

A data transmission method for use with a spatial division multiplexing system comprising at least an optical line terminal, a mode multiplexer, a mode demultiplexer, an optical splitter, and an optical network unit, wherein the optical line terminal is connected to the mode multiplexer by using a single-mode optical fiber, the mode multiplexer is connected to the mode demultiplexer by using a few-mode optical fiber, the mode demultiplexer is connected to the optical splitter by using a single-mode optical fiber, the optical splitter is connected to the optical network unit, and a quantity of modes to which optical signals transmitted in the few-mode optical fiber belong is between a quantity of modes supported by a multimode optical fiber and a quantity of modes supported by the single-mode optical fiber, the method comprising:

• upon startup of the optical line terminal, transmitting, by the optical line terminal, a first training sequence to the optical network unit;
• estimating, by the optical line terminal, a first crosstalk channel coefficient of first crosstalk on a first link from the optical line terminal to the optical network unit according to the first training sequence, wherein the first crosstalk on the first link from the optical line terminal to the optical network unit is crosstalk caused to the first link by an optical signal on a second link that shares a same few-mode optical fiber with the first link and that is from one or more other optical line terminals to one or more other optical network units;
• obtaining, by the optical line terminal, a pre-emphasis coefficient according to the estimated first crosstalk channel coefficient;
• and
• performing, by the optical line terminal according to the pre-emphasis coefficient, pre-emphasis on a to-be-transmitted optical signal on the first link to eliminate crosstalk.

An optical line terminal, comprising:

• a first transmitter, configured to:
• upon startup of the optical line terminal, transmit a first training sequence to the optical network unit, and
• transmit the pre-emphasized optical signal according to an instruction from a second processor;
• and
• wherein the second processor is configured to:
• estimate a first crosstalk channel coefficient of first crosstalk on a first link from the optical line terminal to the optical network unit according to the first training sequence, wherein the first crosstalk on the first link from the optical line terminal to the optical network unit is crosstalk caused to the first link by an optical signal on a second link that shares a same few-mode optical fiber with the first link and that is from one or more other optical line terminals to one or more other optical network units,
• obtain a pre-emphasis coefficient according to the estimated first crosstalk channel coefficient,
• perform pre-emphasis on a to-be-transmitted optical signal on the first link according to the pre-emphasis coefficient, and
• instruct the first transmitter to transmit the pre-emphasized optical signal.

A data communications apparatus comprising:

• a processor;
• and
• a memory, coupled to the processor via a bus system, configured to store instructions which, when executed by the processor, cause the processor to:
• receive, from an input port, a first optical signal transmitted by an optical line terminal,
• convert, according to a correspondence between an input port of an optical signal and a mode of the optical signal, the received first optical signal into a second optical signal in a mode corresponding to the input port, and
• multiplex the second optical signal obtained by means of conversion to a few-mode optical fiber for transmission, wherein a quantity of modes supported by the few-mode optical fiber is between a quantity of modes supported by a multimode optical fiber and a quantity of modes supported by a single-mode optical fiber.

A data communications apparatus comprising:

• a processor;
• and
• a memory, coupled to the processor via a bus system, configured to store instructions which, when executed by the processor, cause the processor to:
• upon startup of an optical line terminal, transmit a first training sequence to an optical network unit,
• estimate a first crosstalk channel coefficient of first crosstalk on a first link from the optical line terminal to the optical network unit according to the first training sequence, wherein the first crosstalk on the first link from the optical line terminal to the optical network unit is crosstalk caused to the first link by an optical signal on a second link that shares a same few-mode optical fiber with the first link and that is from one or more other optical line terminals to one or more other optical network units,
• obtain a pre-emphasis coefficient according to the estimated first crosstalk channel coefficient, and
• perform pre-emphasis on a to-be-transmitted optical signal on the first link according to the pre-emphasis coefficient to eliminate crosstalk.