Patent Description:
With the continuous development of laser technology, laser devices are more and more widely applied to general technologies of various fields of modern society, and play important roles in communication, medical treatment, machining, radar, material processing and the like. Optical power detector is one of the key technologies in the laser device, which plays a role in photoelectric conversion of output optical signals in the device, and is an important part of a laser control loop, and optical signal detection is an essential and important link of the whole laser device system.

Current optical power detectors used in the market include two independent functional units, i.e., a light splitting unit and a photodetection unit. The light splitting unit splits the emitted optical signal into two beams, one being output for external application, and the other being provided to the photodetection unit. The photodetection unit provides the detected optical signal to a light source control device which uses the optical signal detected by the photodetection unit in a negative feedback loop, so as to control the light source to output a stable and satisfactory laser source.

In applications, the main optical power of the light source device is assigned to an optical output port of the device, and only a small proportion of the optical power is input to the photodetector, resulting in a very weak electric signal output by the photodetector. Thus, an external amplifier is required to amplify the weak electrical signal. However, the external amplifier unit is easily interfered by other strong electromagnetic signals, and if the interference signals are crossed into the control loop of the light emitting unit, normal work of the control device of the light emitting unit will be affected so that the control device of the light emitting unit cannot work stably at a set locking point, resulting in unlocking of the working point. The unlocking of the working point may cause instability of the overall light emitting device, and it is externally shown as failure of the light emitting device.

In order to reduce the influence of interference, a metal shield for shielding electromagnetic interference needs to be additionally arranged. This kind of external shield needs to be installed manually, and is low in production efficiency, high in cost and unstable in working efficiency.

US Patent Application, <CIT>, titled "Optical fiber pressure transducer" discloses an optical fiber pressure transducer including a light source for emitting light along an optical axis defined by an optical fiber along a path so that the light strikes and is then reflected back from a mirror. The reflected light is transmitted by way of the same optical fiber and is diverted, as by a beam splitter, to a light detector. The light detector serves to measure the amount of the light reflected by mirror. The amount of light reflected back into the optical fiber is varied in dependence upon the position of a shutter located intermediate the distal end of the fiber and the mirror. Shutter is mounted to or fabricated as a contiguous part of a polymeric membrane which deflects in response to blood pressure acting on the membrane in a direction, as indicated by the arrow, which is transverse to the axis of fiber. As the blood pressure increases, the shutter interrupts more and more light and this is measured by the light detector.

According to an aspect of the disclosure, there is provided an optical power detection apparatus according to claim <NUM>.

Accompanying drawings are provided for further understanding of the embodiments of the disclosure and constitute a part of the specification. Hereinafter, these drawings are intended to explain the disclosure together with the following embodiments, but should not be considered as a limitation to the disclosure. In the drawings:.

Implementations, functions, features and advantages of the present disclosure will be further explained below with reference to the embodiments and the accompanying drawings.

For clarity and better understanding of the technical problems, technical solutions and beneficial effects of the present disclosure, the present disclosure will be further described in detail below in conjunction with the accompanying drawings and embodiments. It will be appreciated that the specific embodiments described herein are merely for illustration of the disclosure and are not intended to limit the disclosure.

In the following description, elements described using terms, such as "module", "component" or "unit", are only used for facilitating description of the present disclosure, and have no specific meaning in themselves. Thus, "module", "component" or "unit" may be used interchangeably.

<FIG> is a schematic structural diagram of an optical power detection device according to an embodiment of the present disclosure not according to the claims.

As shown in <FIG>, the optical power detection device according to an embodiment of the present disclosure includes an optical splitter <NUM>, a photocell <NUM>, an electrical amplification module <NUM>, and a micro-shield <NUM>. The photocell <NUM> and the electrical amplification module <NUM> may be integrated.

The optical splitter <NUM> splits an input optical signal into a first optical signal and a second optical signal at a preset fixed proportion; and adjusts the proportion as needed. The proportion is not changeable any more after being determined, and it may be considered that the output optical power and the total input optical signal power are linearly proportional. The first optical signal is used as an input signal of an optical detection branch, and the second optical signal is used for output.

The photocell <NUM> is connected to an output end of the optical splitter <NUM> for outputting the first optical signal. The photocell <NUM> receives the first optical signal output by the optical splitter <NUM>, and converts the first optical signal into a current signal. The photocell <NUM> may be a photodiode device for converting light energy into electric energy. For example, a PN junction photodiode may utilize the photosensitive property of the PN junction to convert the received light change into a current change.

The micro-shield <NUM> encapsulates the photocell <NUM> and the electrical amplification module <NUM>. Since the current output by the photocell <NUM> is very weak, the electrical amplification module <NUM> works in a weak small-signal state in which the current-voltage conversion process is easily interfered by external high-frequency signals. In this embodiment, the photocell <NUM> and the electrical amplification module <NUM> are encapsulated in the micro-shield <NUM> as a whole, so as to prevent external interference from affecting output of the voltage signal. The micro-shield <NUM> may shield interference of external electromagnetic signals.

<FIG> is a current-voltage characteristic curve of a photocell according to an embodiment of the disclosure.

Referring to <FIG>, in the absence of illumination, the photocell, like a common diode, has unidirectional conductivity, and when a forward voltage is applied externally, the current and the terminal voltage have an exponential relationship; when a reverse voltage is applied externally, the reverse current is called dark current and is generally less than <NUM> nA. In the presence of illumination, the characteristic curve moves downward. The characteristic curve is a set of parallel lines of the horizontal axis over a certain range of reverse voltages. The current generated by the photocell under illumination at the reverse voltage is called photocurrent, which is controlled by the incident light intensity. When the light intensity is constant, an optical detector may be equivalent to a constant current source. The greater the light intensity, the greater the photocurrent, and the photocurrent has a linear relationship with the light intensity when the photocurrent is greater than tens of microamperes.

Since the photoelectric conversion efficiency of the photodiode device directly affects the product performance, this index is generally required to be greater than <NUM> a/w. In addition, in order to reduce background noise interference, the dark current index is not greater than <NUM> nA. To expand the dynamic range of the input optical signal, the photocell is reversely biased.

Returning to <FIG>, the electrical amplification module <NUM> is connected to an output end of the photocell <NUM> for outputting current signals, receives the current signal output by the photocell <NUM>, converts the current signal into a voltage signal, and performs gain processing on and then outputs the voltage signal.

The micro-shield <NUM> may have, for example, a disc or cylindrical shape, but the embodiment of the present disclosure is not limited thereto. In a specific implementation, the micro-shield <NUM> may be provided with an optical communication via and an electrical communication via. The optical communication via is used for installation of a convex lens or passing of an optical fiber, thereby transmitting the first optical signal to the photocell <NUM>. The optical fiber may include a tapered optical fiber. The electrical communication via is used for passing of a power supply wire or a pin, so as to transmit the gain-processed voltage signal.

<FIG> is a schematic structural diagram of an electrical amplification module according to an embodiment of the disclosure.

As shown in <FIG>, the electrical amplification module <NUM> according to an embodiment of the disclosure may include a pre-amplifier <NUM> connected to an anode of the photocell <NUM> via a PDA pin, and a post-amplifier <NUM> connected to the pre-amplifier <NUM>.

The pre-amplifier <NUM> converts the current signal output by the photocell <NUM> into a voltage signal through a feedback resistor <NUM>. The pre-amplifier <NUM> may also control the gain of the voltage signal by changing the resistance of the feedback resistor <NUM>.

In an embodiment of the present disclosure, a power supply may supply power to the pre-amplifier <NUM> via a VCC pin and a voltage regulator <NUM>, so as to reduce power supply noise interference. The power supply may also be connected to a cathode of the photocell <NUM> via a voltage regulator <NUM> and a PDC pin.

The post-amplifier <NUM> performs gain processing on the voltage signal converted by the pre-amplifier <NUM>. To increase the dynamic range of the input signal and maintain a fixed signal output range, the gain of the post-amplifier <NUM> is processed by an Automatic Gain Control (AGC) unit.

In an embodiment of the present disclosure, the electrical amplification module <NUM> may further include a low frequency feedback loop unit <NUM> and a Received Signal Strength Indication (RSSI) unit <NUM> connected to the low frequency feedback loop unit <NUM>. The low frequency feedback loop unit <NUM> is connected to the post-amplifier <NUM> to eliminate a DC signal component in an input signal of the electrical amplification module <NUM>. The signal output by the post-amplifier <NUM> is output after the DC signal component is removed by the low frequency feedback loop unit <NUM>. The low frequency feedback loop unit <NUM> may include a DC restorer, and two resistors connected to the DC restorer.

<FIG> is a schematic structural diagram of an optical power detection apparatus according to an embodiment of the present disclosure.

As shown in <FIG>, the optical power detection apparatus according to an embodiment of the present disclosure includes the optical power detection device <NUM> according to the embodiments of the present disclosure, and at least one of a phase bias control unit <NUM> and an optical power control unit <NUM>. The phase bias control unit <NUM> and the optical power control unit <NUM> are respectively connected to the optical power detection device <NUM>, and respectively receive a voltage signal output by the optical power detection device <NUM>.

Typically, a phase bias control unit <NUM> may be connected to a modulator to adjust a phase bias working point of the modulator. The optical power control unit <NUM> may be connected with a variable optical attenuator, and the output optical signal power is adjusted by controlling an attenuation value of the variable optical attenuator.

The optical power detection device according to the embodiment of the disclosure may be applied to a PM-QPSK transmitter, an erbium-doped fiber amplifier, a PM-16QAM transmitter and the like.

<FIG> is a schematic structural diagram of a PM-QPSK transmitter including an optical power detection device according to an embodiment of the present disclosure.

As shown in <FIG>, in an optical transmitter for implementing a <NUM> Gbit/s highspeed optical transmission device, the transmitter using a Mach-Zehnder type modulator is a transmitter based on a PM-QPSK modulation device. A bias voltage of a modulator <NUM> is controlled by a pilot signal plus a DC value.

The optical input to the modulator <NUM> uses a tunable laser (ITLA) <NUM> as a light source, and optical signals of continuous wavelengths emitted by the ITLA <NUM> are modulated by the modulator <NUM> to form optical output signals in an optical PM-QPSK modulation format. The data input to modulator <NUM> are <NUM>-way signals output from a PM-QPSK signal source (not shown).

The modulated optical signal output by the modulator <NUM> is input to an optical power detection device <NUM>. The optical power detection device <NUM> may be an optical power detection device according to the embodiments of the present disclosure. The optical power detection device <NUM> splits the modulated optical signal into two parts, i.e., a first optical signal and a second optical signal. The second optical signal is coupled into an output port of the optical power detection device <NUM>, i.e., a <NUM> network-side optical output port, as a main output signal. The first optical signal is coupled into the photocell <NUM>, and the photocell <NUM> and the electrical amplification module <NUM> are disposed in the micro-shield <NUM> (see <FIG>) to convert the input optical signal into a photocurrent, and then into a voltage signal for amplification. The amplitude of the voltage signal is in a proportional relationship with the total input optical signal power of the optical power detection device <NUM>, and may reflect the magnitude of the total input optical power, so that the output optical signal power may be adjusted by controlling an attenuation value of the variable optical attenuator. The output of the electrical amplification module <NUM> in the optical power detection device <NUM> is transmitted to the phase bias control unit <NUM> to adjust a phase bias working point of the modulator <NUM>.

<FIG> is a schematic structural diagram of an erbium-doped fiber amplifier including an optical power detection device according to an embodiment of the present disclosure.

As shown in <FIG>, the erbium-doped fiber amplifier includes: optical isolators <NUM>, <NUM>, <NUM> and <NUM>; <NUM>/<NUM> wavelength division multiplexers (WDMs) <NUM>, <NUM>; <NUM> pump lasers <NUM>, <NUM>; erbium-doped fibers <NUM> and <NUM>, variable optical attenuators <NUM> and <NUM>, an optical power detection device <NUM>, an optical power control unit <NUM>, and a Micro Control Unit (MCU) <NUM>. The optical isolator <NUM>, the wavelength division multiplexer <NUM>, the erbium-doped fiber <NUM>, the optical isolator <NUM>, the variable optical attenuator <NUM> and the optical power detection device <NUM> are connected in sequence. The pump laser <NUM> is connected to the wavelength division multiplexer <NUM> to deliver energy to the erbium-doped fiber <NUM>. The optical power control unit <NUM> is connected to an output end of the optical power detection device <NUM> and the MCU <NUM>, respectively. The optical isolator <NUM>, the wavelength division multiplexer <NUM>, the erbium-doped fiber <NUM>, the optical isolator <NUM>, the variable optical attenuator <NUM> and the optical power detection device <NUM> are connected in sequence. The pump laser <NUM> is connected to the wavelength division multiplexer <NUM> to deliver energy to the erbium-doped fiber <NUM>. The optical power control unit <NUM> is connected to an output end of the optical power detection device <NUM> and the MCU <NUM>, respectively. In actual use, for two groups of input optical signals, one reaches the optical power detection device <NUM> via the optical isolator <NUM>, the wavelength division multiplexer <NUM>, the erbium-doped fiber <NUM>, the optical isolator <NUM> and the variable optical attenuator <NUM>, and the other reaches the optical power detection device <NUM> via the optical isolator <NUM>, the wavelength division multiplexer <NUM>, the erbium-doped fiber <NUM>, the optical isolator <NUM> and the variable optical attenuator <NUM>.

In this embodiment, a <NUM> optical signal is added from the input end, and energy from the <NUM> pump laser is received in the erbium-doped fiber so that stimulated radiation is produced and a <NUM> optical signal with an enhanced power is output.

Part of the optical signals split out by the optical power detection device <NUM> is used for detecting strength of the optical signals, and the rest optical signals are coupled into to the output port for transmission of the optical signals. The optical signal detected by the optical power detection device <NUM> is converted into an electrical signal, and then input to the optical power control units <NUM> and <NUM> as a negative feedback signal to control the variable optical attenuators <NUM> and <NUM> to output satisfactory optical signal strength.

The optical power detection device <NUM> may be an optical power detection device according to the embodiments of the present disclosure.

<FIG> is a schematic structural diagram of a PM-16QAM transmitter including an optical power detection device according to an embodiment of the present disclosure.

As shown in <FIG>, in a <NUM> PM-16QAM transmitter, an optical input to a modulator <NUM> uses a tunable laser, ITLA <NUM>, as a light source. Optical signals of continuous wavelengths emitted by the ITLA <NUM> are modulated by the modulator <NUM> to form optical output signals in an optical 16QAM modulation format. The data input to the modulator <NUM> are signals amplified by a driver <NUM> from signals output of a two-channel <NUM>-way signal source (not shown).

The modulated optical signal output from the modulator <NUM> enters an optical power detection device <NUM> through a variable optical attenuator <NUM>. The optical power detection device <NUM> splits the modulated optical signal into two parts, one is coupled into an output port of the optical power detection device <NUM>, i.e., a <NUM> network-side optical output port, as a main output signal; and the other is coupled into the photocell <NUM>, and the photocell <NUM> and the electrical amplification module <NUM> are disposed in the micro-shield <NUM> (see <FIG>) to convert the input optical signal into a photocurrent, and then into a voltage signal for amplification. The amplitude of the voltage signal is in a proportional relationship with the total input optical signal power of the optical power detection device <NUM>, and may reflect the magnitude of the total input optical power. The voltage signal is output to the optical power control unit <NUM> so that the output optical signal power may be adjusted by controlling an attenuation value of the variable optical attenuator <NUM>. Further, the output of the electrical amplification module <NUM> in the optical power detection device <NUM> is transmitted to the phase bias control unit <NUM> to adjust a phase bias working point of the modulator <NUM>.

The present disclosure provides an optical power detection device in which the photocell and the electrical amplification module are encapsulated in the micro-shield to protect signals of the photocell and the electrical amplification module from external interference, thereby effectively saving material cost of the external shield as well as labor cost of welding and installation. In the present disclosure, the optical splitter, the photocell and the electrical amplification module are integrated, thereby improving the sensitivity and integration level while reducing the number of devices, and thus facilitating layout and wiring.

Claim 1:
An optical power detection apparatus, comprising:
a modulator configured to modulate an optical signal of a light source to output a modulated optical signal;
an optical power detection device (<NUM>) comprising:
an optical splitter (<NUM>) configured to receive the modulated optical signal and split the modulated optical signal into a first optical signal and a second optical signal at a preset fixed proportion, the second optical signal being coupled into an output port of the optical power detection device as a main output signal;
a photocell (<NUM>) connected to an output end of the optical splitter (<NUM>), the photocell (<NUM>) being configured to receive the first optical signal output by the optical splitter (<NUM>) and convert the first optical signal into a current signal;
an electrical amplification module (<NUM>) connected to an output end of the photocell (<NUM>), the electrical amplification module (<NUM>) being configured to receive the current signal output by the photocell (<NUM>), convert the current signal into a voltage signal, and perform gain processing on and then output the voltage signal; and
a micro-shield (<NUM>) configured to encapsulate the photocell (<NUM>) and the electrical amplification module (<NUM>); characterized in that the optical power detection apparatus further comprises
a phase bias control unit (<NUM>) connected to the optical power detection device (<NUM>) and the modulator, and configured to receive a voltage signal output by the optical power detection device (<NUM>) and to adjust a phase bias working point of the modulator.