Patent Description:
Fiber-optic communication has revolutionized the telecommunications industry and the data networking community. Using optical fibers to transmit optical signals from one place to another, fiber-optic communications have enabled telecommunications links to be made over much greater distances, with much higher data rates and with higher security. As a result of these advantages, fiber-optic communication systems are widely employed for applications ranging from major telecommunications backbone infrastructure to Ethernet systems, broadband distributions, and general data networking.

Among various types of fiber-optic communication systems, there are typically three major components: optical fibers and optical cables made thereof, active optical devices, and passive optical devices. In the structure of a fiber-optic communication system, an optical transceiver is an active optical device configured to integrate the function of a transmitter and a receiver. An electrical-to-optical transceiver at the transmitting end is able to generate optical signals from electrical signals for subsequent data transmission. A corresponding optical-to-electrical transceiver at the receiving end is able to convert the optical signals received from the transceiver into the original electrical signals.

An optical transceiver normally adopts laser diodes (LDs) or light-emitting diodes (LEDs) as lighting devices for providing optical signals. The electrical-to-optical conversion efficiency of the optical transceiver is associated with the performance of its lighting device whose operational efficiency may be downgraded in a high-temperature industrial environment. In a prior art application, the optical transceiver is normally configured to transmit signals using a maximum optical transmitting power defined by its specification. If the optical transmitting power of the optical transceiver can be reduced while ensuring normal communication, the operational current can be greatly decreased for reducing the heat during the electrical-to-optical conversion, thereby slowing down the aging process of light devices and prolonging the lifespan.

<CIT> teaches an adaptive power setting techniques for optical transceivers are provided. Optical signals are received at a first optical transceiver device that are transmitted from a second optical transceiver device. A receive power of the optical signals received at the first optical transceiver device from the second optical transceiver device is determined. A characteristic of optical signals transmitted by the first optical transceiver device to the second optical transceiver device is modulated to indicate to the second optical transceiver device a disparity of the receive power with respect to a target receive power level at the first optical transceiver device. Conversely, the first optical transceiver device adjusts a power level of optical signals transmitted by the first optical transceiver device to the second optical transceiver device based on a characteristic of the optical signals received at the first optical transceiver device.

The present invention aims at providing a method of performing dynamic power optimization in a fiber-optic communication system in response to poor connection or bad communication quality associated with a link-on event of the fiber-optic communication system and the related fiber-optic communication system.

This is achieved by a method of performing dynamic power optimization in a fiber-optic communication system according to claim <NUM> and by a fiber-optical communication system according to claim <NUM>. The dependent claims pertain to corresponding further developments and improvements.

As will be seen more clearly from the detailed description following below, the claimed method of performing dynamic power optimization in a fiber-optic communication system in response to poor connection or bad communication quality associated with a link-on event of the fiber-optic communication system includes a first optical transceiver in the fiber-optic communication system transmitting a power correction request packet to a second optical transceiver in the fiber-optic communication system using an optical transmitting power having an initial value, acquiring a power compensation value which is associated with an optical receiving power actually inputted into the second optical transceiver and an expected input power of the second optical transceiver, adjusting the optical transmitting power according to the power compensation value when a value of the optical receiving power is larger than a value of the expected input power, and the first optical transceiver transmitting signals to the second optical transceiver using the adjusted optical transmitting power.

As will be seen more clearly from the detailed description following below, the claimed fiber-optic communication system which performs dynamic power optimization in response to poor connection or bad communication quality associated with a link-on event of the fiber-optic communication system includes a first optical transceiver, a first operation control unit, a second optical transceiver, and a second operation control unit. The first optical transceiver includes a first TOSA configured to transmit a signal using an optical transmitting power, a first ROSA, and a first power monitor circuit configured to monitor an operational status of the first optical transceiver. The first operation control unit is configured to adjust a value of the optical transmitting power. The second optical transceiver includes a second TOSA, a second ROSA configured to receive the signal transmitted by the first optical transceiver, and a second power monitor circuit configured to monitor an optical receiving power which is actually inputted into the second optical transceiver. The second operation control unit is configured to determine whether a value of the optical receiving power is larger than an expected input power of the second optical transceiver, and provide the optical receiving power and the expected input power for acquiring a power compensation value when determining that the value of the optical receiving power is larger than the value of the expected input power.

<FIG> is a functional diagram illustrating a fiber-optic communication system <NUM> according to an embodiment of the present invention. <FIG> is a functional diagram illustrating a fiber-optic communication system <NUM> according to another embodiment of the present invention. Each of the fiber-optic communication systems <NUM> and <NUM> includes a plurality of optical transceivers capable of transmitting optical signals using optical fibers. Each optical transceiver is configured to convert electrical signals into optical signals using electrical-to-optical conversion, and then transmit the optical signals to another optical transceiver using optical fibers. After receiving optical signals from another optical transceiver, each optical transceiver may convert the received optical signals into electrical signals using optical-to-electrical conversion, thereby supplying other electronic equipment. For illustrative purpose, <FIG> and <FIG> depict the embodiment of two optical transceivers. However, the number of optical transceivers in the fiber-optic communication system <NUM> or <NUM> does not limit the scope of the present invention.

Each of the fiber-optic communication systems <NUM> and <NUM> includes an optical transceiver 100A, an optical transceiver 100B, an operation control unit 60A, an operation control unit 60B, and two optical fibers <NUM> and <NUM>. The optical transceiver 100A includes a transmitter optical sub-assembly (TOSA) TOSA_A, a receiver optical sub-assembly (ROSA) ROSA_A, a transmitting-end driving circuit 30A, a receiving-end amplifying circuit 40A, and a power monitor unit 50A. The optical transceiver 100B includes a transmitter optical sub-assembly TOSA_B, a receiver optical sub-assembly ROSA_B, a transmitting-end driving circuit 30B, a receiving-end amplifying circuit 40B, and a power monitor unit 50B. The transmitter optical sub-assembly TOSA_A of the optical transceiver 100A may transmit optical signals to the receiver optical sub-assembly ROSA_B of the optical transceiver <NUM> using the optical fiber <NUM>. The transmitter optical sub-assembly TOSA_B of the optical transceiver 100B may transmit optical signals to the receiver optical sub-assembly ROSA_A of the optical transceiver <NUM> using the optical fiber <NUM>.

In the fiber-optic communication system 100A depicted in <FIG>, the operation control unit 60A and the optical transceiver 100A are two stand-alone devices, and the operation control unit 60B and the optical transceiver 100B are two stand-alone devices. In the fiber-optic communication system 100B depicted in <FIG>, the operation control unit 60A is integrated into the optical transceiver 100A, and the operation control unit 60B is integrated into the optical transceiver 100B. However, the implementations of the operation control units 60A and 60B do not limit the scope of the present invention.

Each of the transmitter optical sub-assemblies TOSA_A and TOSA_B includes lighting devices, photo detectors, optical mirrors and structural devices (not shown in <FIG> and <FIG>) such as ferrules, sleeves, housings and transistor outline cans (TO-Cans). In the optical transceivers 100A and 100B, the lighting devices in the transmitter optical sub-assemblies TOSA_A and TOSA_B can convert electrical signals into optical signals, which are then directed into the corresponding optical fiber by a focusing device for data transmission. In the embodiments of the present invention, the lighting devices in the transmitter optical sub-assemblies TOSA_A and TOSA_B may be LDs or LEDs, such as using Fabry-Perot LDs, distributed feedback (DFB) LDs, vertical-cavity surface-emitting laser (VCSEL) diodes, fiber Bragg grating (FBG) LDs, GaAs LEDs or GaAsP LEDs for providing optical signals with various modulations, wavelengths, speeds and output power. However, the types of the lighting devices in the transmitter optical sub-assemblies TOSA_A and TOSA_B do not limit the scope of the present invention.

Each of the receiver optical sub-assemblies ROSA_A and ROSA_B includes light-detecting devices, transimpedance amplifier, optical mirrors and structural devices (not shown in <FIG> and <FIG>) such as ferrules, sleeves, housings and TO-Cans. In the optical transceivers 100A and 100B, optical signals transmitted via the optical fibers may be directed into the light-detecting devices of the receiver optical sub-assemblies ROSA_A and ROSA_B and then converted into electrical signals. In the embodiments of the present invention, the light-detecting devices in the receiver optical sub-assemblies ROSA_A and ROSA_B may be PIN photodiodes, avalanche photodiodes (APD) or metal-semiconductor-metal (MSM) photodiodes. However, the types of the light-detecting devices in the receiver optical sub-assemblies ROSA_A and ROSA_B do not limit the scope of the present invention.

The transmitting-end driving circuits 30A and 30B are configured to provide driving signals for operating the lighting devices in the transmitter optical sub-assemblies TOSA_A and TOSA_B, respectively. The receiving-end amplifying circuits 40A and 40B are configured to amplify the signals outputted by the light-detecting devices in the receiver optical sub-assemblies ROSA_A and ROSA_B, respectively.

<FIG> is a diagram illustrating the implementation of the transmitting-end driving circuit in each optical transceiver of the fiber-optic communication system <NUM> or <NUM> according to an embodiment of the present invention. Each transmitting-end driving circuit includes a differential transistor pair TR, a balancing load RB, a modulated current source IMOD, a bias current source IBIAS, a damping resistor RD, an output inductor LOUT, and a bias inductor LBIAS. Each transmitting-end driving circuit is configured to provide driving current ILASER for operating the lighting device in the corresponding TOSA according to an input voltage VIN, wherein ILASER=IBIAS+IMOD. However, the implementation of the transmitting-end driving circuit in each optical transceiver does not limit the scope of the present invention.

<FIG> is a diagram illustrating related waveforms during the operation of the transmitting-end driving circuit in each optical transceiver of the fiber-optic communication system <NUM> or <NUM> according to an embodiment of the present invention. For illustrative purpose, it is assumed that each TOSA adopts a laser diode as its lighting device. The vertical axis represents TOSA output power, the horizontal axis represents current, CHR represents the characteristic curve of the laser diode, TxP represents the optical transmitting power of the TOSA, and ILASER represents the driving current provided by the transmitting-end driving circuit. When the driving current ILASER is not larger than a threshold current ITH, the laser diode generates photons by spontaneous emission and thus has a small optical transmitting power TxP. When the driving current ILASER is larger than the threshold current ITH, stimulated emission starts to dominate the coherent optical output of the laser diode, wherein the intensity of stimulation rapidly increases in response to an increase in the driving current ILASER. In order to prevent the time delay between the logic <NUM> and logic <NUM> outputs of the laser due to intense stimulated emission, each transmitting-end driving circuit is configured to provide a constant bias current IBIAS for the logic <NUM> output, wherein the value of the bias current IBIAS is larger than the value of the threshold current ITH, and ILASER=IBIAS. For the logic <NUM> output, each transmitting-end driving circuit is further configured to provide the modulated current IMOD which is switched on or off based on the input signal, wherein ILASER= IBIAS+IMOD.

The power monitor unit 50A is configured to monitor the optical transmitting power TxP_A of the transmitter optical sub-assembly TOSA_A and the optical receiving power RxP_A of the receiver optical sub-assembly ROSA_A. The power monitor unit 50B is configured to monitor the optical transmitting power TxP_B of the transmitter optical sub-assembly TOSA_B and the optical receiving power RxP_B of the receiver optical sub-assembly ROSA_B.

<FIG> is a diagram illustrating the relationship between the data monitored by each power monitor unit in the fiber-optic communication system <NUM> or <NUM> according to an embodiment of the present invention. For illustrative purpose, it is assumed that the optical transceiver 100A is a transmitting-end device and the optical transceiver 100B is a receiving-end device. When the transmitter optical sub-assembly TOSA_A in the optical transceiver 100A transmits data using the optical transmitting power TxP_A, the optical receiving power RxP_B is the actual input power of the receiver optical sub-assembly ROSA_B in the optical transceiver 100B. There are two main loss mechanisms in an optical fiber: internal loss (material scattering loss, material absorption loss or waveguide scattering loss) and external loss (bending attenuation loss, micro bending attenuation loss, connection loss or manufacturing damage loss). As a result of a path loss PL due to the above-mentioned loss mechanisms, the received power of a receiving-end device is lower than the output power of a transmitting-end device, wherein PL=TxP_A-RxP_B.

Also, the optical transceiver 100B may have different settings of input sensitivity PIS for different brands of the receiver optical sub-assembly ROSA_B, while a power budge PB may reflect the degree of power attenuation due to the aging of internal devices of the optical transceiver 100B and the aging of optical fibers. The values of the input sensitivity PIS and the power budge PB may be set manually by the user or automatically by the system for different applications. The expected input power ExP_B of the optical transceiver 100B may be determined according to the input sensitivity PIS and the power budge PB, wherein ExP_B=PIS+PB. As depicted in <FIG>, when the optical receiving power RxP_B actually inputted into the optical transceiver 100B is larger than its expected input power ExP_B, an amount of power equal to a power compensation value ΔTxP is wasted, wherein ΔTxP=RxP_B-ExP_B.

In the present invention, the optical transceiver 100A may adjust the optical transmitting power TxP_A of its transmitter optical sub-assembly TOSA_A so as to make the power compensation value ΔTxP as small as possible while ensuring normal communication. Assuming that the initial value of the optical transmitting power TxP_A of the optical transceiver 100A is represented by TX0, the value of the optical transmitting power TxP_A after each adjustment may be represented by T1, wherein TX1=TX0-ΔTxP+n*ΔP, n is the number of fine-tune step, and ΔP represents the fine-tune amount of each fine-tune step.

<FIG> is a flowchart illustrating the operation of the fiber-optic communication system <NUM> or <NUM> according to an embodiment of the present invention. For illustrative purpose, it is again assumed that the optical transceiver 100A of the fiber-optic communication system <NUM> or <NUM> is a transmitting-end device capable of transmitting signals to the optical transceiver 100B on the receiving end using the fiber <NUM>. The flowchart in <FIG> includes the following steps:.

In response to poor connection or bad communication quality associated with an link-on event of the fiber-optic communication system <NUM> or <NUM> (such as when detecting an increase in CRC), the power correction procedure may be initiated in step <NUM> for acquiring an optimized power setting. For illustrative purpose, it is assumed that in the fiber-optic communication system <NUM> or <NUM>, the optical transceiver 100A is a transmitting-end device and the optical transceiver 100B is a receiving-end device.

In step <NUM>, the optical transceiver 100A is configured to set the value of the fine-tune step n to <NUM> and set the optical transmitting power TxP_A to the initial value TX0. In step <NUM>, the optical transceiver 100A is configured to send the power correction request packet to the optical transceiver 100B via the fiber <NUM> using the optical transmitting power TxP_A having the initial value TX0. In an embodiment, the initial value TX0 is equal to a maximum optical transmitting power of the transmitter optical sub-assembly TOSA_A in the optical transceiver 100A defined by its specification. In another embodiment, the initial value TX0 may be equal to any value which is not larger than the maximum optical transmitting power of the transmitter optical sub-assembly TOSA_A in the optical transceiver 100A. However, the method of setting the initial value TX0 does not limit the scope of the present invention.

After receiving the power correction request packet from the optical transceiver 100A, the optical transceiver 100B is able to acquire the optical receiving power RxP_B actually inputted into the optical transceiver 100B. Then in step <NUM>, the optical transceiver 100B is configured to send the power correction reply packet which includes the values of the optical receiving power RxP_B and the expected input power ExP_B to the optical transceiver 100A via the fiber <NUM>.

In step <NUM>, after receiving the power correction reply packet from the optical transceiver 100B, the optical transceiver 100A is configured to determine whether the optical receiving power RxP_B is larger than the expected input power ExP_B. When the optical receiving power RxP_B is larger than the expected input power ExP_B, the difference between the values of the optical receiving power RxP_B and the expected input power ExP_B results in a waste of power. Under such circumstance, the optical transceiver <NUM> is configured to acquire the power compensation value ΔTxP according to the values of the optical receiving power RxP_B and the expected input power ExP_B in step <NUM>, wherein ΔTxP=RxP_B-ExP_B. When determining that the optical receiving power RxP_B is not larger than the expected input power ExP_B, it indicates that the optical transceiver 100A may have an abnormal optical transmitting power TxP_A, or that a large path loss PL exists between the optical transceiver 100A and the optical transceiver 100B. Under such circumstance, step <NUM> is executed for ending the power correction procedure.

In step <NUM>, the optical transceiver 100A is configured to set the value of its optical transmitting power TxP_A to the adjusted value TX1 and transmit the test packet to the optical transceiver 100B using the adjusted optical transmitting power TxP_A for performing the verification procedure, wherein TX1=TX0-ΔTxP+n*ΔP. After having executed step <NUM> for the first time, the value of the fine-tune step n is equal to <NUM> which was set in step <NUM>. Under such circumstance, the value of the adjusted value TX1 is equal to the initial value TX0 subtracted by the power compensation value ΔTxP.

As depicted in <FIG>, the path loss PL existing between the optical transceiver 100A and the optical transceiver 100B may result in extra power consumption whose value may be influence by many factors. Therefore, the optical transceiver 100A is configured to perform the verification procedure in steps <NUM>-<NUM> to ensure that data can be successfully transmitted using the optical transmitting power TxP_A having the adjusted value TX1.

In step <NUM>, the optical transceiver 100A is configured to transmit the test packet to the optical transceiver 100B using the optical transmitting power TxP_A having the adjusted value TX1. After receiving the test packet, the optical transceiver 100B is configured to perform the verification procedure and notify the optical transceiver 100A if the verification procedure is successful. If the optical transceiver 100A receives the verification successful message from the optical transceiver 100B, step <NUM> may then be executed for ending the power correction procedure. Under such circumstance, the optical transceiver 100A is configured to send signals to the optical transceiver 100B using the optical transmitting power TxP_A having the adjusted value TX1, thereby lowering power consumption while ensuring normal data transmission.

If unable to receive any verification successful message from the optical transceiver 100B, the optical transceiver 100A is configured to increase the value of the fine-tune step n by <NUM> and then determine whether the adjusted value TX1 is larger than the maximum optical transmitting power TPMAX. If the adjusted value TX1 is not larger than the maximum optical transmitting power TPMAX, the present method loops back to step <NUM>.

When executing step <NUM> for the second time, he value of the fine-tune step n is equal to <NUM>, and the value of the adjusted value TX1 is equal to the initial value TX0 subtracted by the power compensation value ΔTxP and plus a fine-tune value ΔP. The optical transceiver 100A may then perform the verification procedure by transmitting the test packet to the optical transceiver 100B using the newly adjusted optical transmitting power TxP_A. When it is determined in step <NUM> that the verification procedure is successful, the optical transceiver 100A is configured to transmit data using the optical transmitting power TxP_A having the adjusted value TX1 equal to TX0-ΔTxP+ΔP.

If the verification procedure is still unsuccessful after executing step <NUM> for the second time, the optical transceiver 100A is configured to re-execute steps <NUM>, <NUM> and <NUM> sequentially. When the fine-tune step n is increased to a value which allows the adjusted value TX1 (TX0-ΔTxP+n*ΔP) to pass the verification procedure in step <NUM>, step <NUM> is then executed for ending the power correction procedure. Under such circumstance, the optical transceiver 100A is configured to transmit data using the optical transmitting power TxP_A having the adjusted value TX1 equal to (TX0-ΔTxP+n*ΔP). If it is determined in the fine-tuning process that the adjusted value TX1 equal to (TX0-ΔTxP+n*ΔP) is larger than the maximum optical transmitting power TPMAX, the optical transceiver 100A is configured to send the connection abnormal warning in step <NUM>.

<FIG> is a flowchart illustrating the operation of the fiber-optic communication system <NUM> or <NUM> according to another embodiment of the present invention. For illustrative purpose, it is again assumed that the optical transceiver 100A of the fiber-optic communication system <NUM> or <NUM> is a transmitting-end device capable of transmitting signals to the optical transceiver 100B on the receiving end using the fiber <NUM>. The flowchart in <FIG> includes the following steps:.

Steps <NUM>-<NUM> and <NUM>-<NUM> depicted in <FIG> are executed in the same manner as steps <NUM>-<NUM> and <NUM>-<NUM> depicted in <FIG>, respectively. The method depicted in <FIG> differs from the method depicted in <FIG> in the execution of steps <NUM>-<NUM> and <NUM>-<NUM>. In the embodiment illustrated in <FIG>, the receiving-end optical transceiver 100B sends the values of its optical receiving power RxP_B and its expected input power ExP_B to the transmitting-end optical transceiver 100A, which then acquires the power compensation value ΔTxP accordingly and determines the value of the power compensation value ΔTxP. In the embodiment illustrated in <FIG>, the receiving-end optical transceiver 100B acquires the power compensation value ΔTxP according to the values of its optical receiving power RxP_B and its expected input power ExP_B, and then sends the power compensation value ΔTxP to the transmitting-end optical transceiver 100A, which then determines the value of the power compensation value ΔTxP.

In the embodiment illustrated in <FIG>, after acquiring the power compensation value ΔTxP according to the values of its optical receiving power RxP_B and its expected input power ExP_B in step <NUM>, the optical transceiver 100B is configured to send the power correction reply packet which includes the power compensation value ΔTxP to the optical transceiver 100A via the fiber <NUM> in step <NUM>. Next, the optical transceiver 100A is configured to determine whether the power compensation value ΔTxP is larger than <NUM> in step <NUM>.

Claim 1:
A method of performing dynamic power optimization in a fiber-optic communication system (<NUM>, <NUM>) in response to poor connection or bad communication quality associated with an event on a link of the fiber-optic communication system (<NUM>, <NUM>) after linking up of a communication channel, comprising:
a first optical transceiver (100A) in the fiber-optic communication system (<NUM>, <NUM>) transmitting a power correction request packet to a second optical transceiver (100B) in the fiber-optic communication system (<NUM>, <NUM>) using an optical transmitting power having an initial value;
characterized by comprising:
acquiring a power compensation value which is associated with a difference between an optical receiving power actually inputted into the second optical transceiver (100B) and an expected input power of the second optical transceiver (100B);
adjusting the optical transmitting power according to the power compensation value when a value of the optical receiving power is larger than a value of the expected input power; and
the first optical transceiver (100A) transmitting signals to the second optical transceiver (100B) using the adjusted optical transmitting power.