WO2014008712A1

WO2014008712A1 - Passive optical network and optical module of optical network unit thereof

Info

Publication number: WO2014008712A1
Application number: PCT/CN2012/081544
Authority: WO
Inventors: 薛登山; 赵其圣; 何鹏
Original assignee: 青岛海信宽带多媒体技术有限公司
Priority date: 2012-07-12
Filing date: 2012-09-18
Publication date: 2014-01-16
Also published as: CN102752676B; CN102752676A

Abstract

A passive optical network and an optical module of an optical network unit thereof are disclosed. The optical network comprises an Optical Line Terminal (OLT), a first Wavelength Division Multiplexing (WDM), a second WDM and a plurality of optical modules of Optical Network Units (ONU), wherein a laser emission unit in the optical module of ONU comprises a Chirp Managed Laser (CML) and a driving circuit thereof. The driving circuit of the laser emission unit is used for receiving electrical signals sent by an ONU system device and driving the CML to emit optical signals with a specific wavelength according to the received electrical signals. The wavelengths of optical signals emitted by different optical modules of ONU are different. The OLT comprises a plurality of laser receiving units which are respectively used for receiving the optical signal with each wavelength, converting the received optical signals into the electrical signals and then sending them to a switch. The CML adopted in the optical module of ONU has better spectrum characteristic, accordingly reducing channel interval and achieving the purposes of supplying more uplink channels and increasing system bandwidth.

Description

Passive optical network and optical network unit optical module

Technical field

The present invention relates to optical fiber communication technologies, and in particular, to a passive optical network and an optical network unit optical module thereof.

Background technique

In the passive optical network shown in FIG. 1, an OLT (Optical Line Terminator) is usually disposed at a central office of an access network system of the optical fiber communication system, and the OLT is responsible for converting electrical signal data in the switch into light. The signal data is sent out, and the externally transmitted optical signal is received and converted into an electrical signal for delivery to the switch. The OLT is connected to the ONU (optical net unit) optical module through the ODN (Optical Feeder Network). The ONU optical module is usually set at the central office, that is, the user end or the building. The splitter is a "split" and generally has 2N equalization. Port, if the input port has a light intensity of 1, the light intensity of each output port is 1/N. For an optical access system, usually one OLT is placed in the telecom central office, and then through the optical splitter, usually at least 1 minute 32, or 1 minute 64 or even 1 minute 128, that is, 1 OLT band 32 or 64 or 128 ONU optical module. Each ONU optical module is connected to an ONU system device for converting electrical signals of the 0NU system device into optical signals for transmission to the OLT in the upstream direction.

With the growing demand for various self-media, such as Weibo and YuTobe, the industry is gradually recognizing the existing EPON (Ethernet Passive Optical Network) and GPON (Gigabit Passive Optical Network). Gigabit Passive Optical Network technology is difficult to meet the long-term development needs of the business, especially in the fiber-to-the-building (FTTB) and fiber-to-the-node (FTTN) scenarios. The optical access network faces new upgrade requirements in terms of bandwidth, service support capabilities, and access node device functions and performance. According to analysis, the demand for upstream bandwidth in users of existing optical networks is growing rapidly.

However, in the prior art passive optical network, although a variety of technical means are used to extend the downlink bandwidth, in the uplink direction of the signal, the ONU optical modules in the optical network all use one wavelength optical signal for signal transmission, that is, It is said that each ONU optical module in the optical network has to multiplex the uplink channel by means of time division multiplexing. Assuming uplink signal transmission rate 20.3125Gbps, in an OLT 128 with the ONU optical module, the optical module 128 multiplexes a ONU upstream channel, each ONU optical module can only be assigned with 10. ³ l ^With a rate of ²⁵ xl/l ²⁸ Gbps, the allocated bandwidth is very limited. At present, although there are 20G PON technologies and WDM technologies in the industry, they are combined to form TWDM PON technology, which further increases the capacity of the system and solves the increasing demand for network bandwidth expansion. However, at present, this WDM PON technology is only based on CWDM's finite wavelength multiplexing (16 wavelengths of full wave, generally only 4 wavelengths of 1320 band), even if DWDM technology is introduced, it is subject to external modulation laser. The characteristics of spectral width and wavelength temperature drift are limited, and the channel spacing is only controlled at 200 GHz intervals (C-band 45 channels).

Therefore, existing optical networks cannot provide sufficient upstream channel bandwidth to meet the growing business demands. Summary of the invention

The embodiments of the present invention provide a passive optical network and an optical network unit optical module for improving the uplink bandwidth of the optical network and the ONU optical module.

According to an aspect of the present invention, a passive optical network is provided, including: an optical line termination optical module OLT, a first wavelength division multiplexer WDM, a second wavelength division multiplexer WDM, and a plurality of ONU optical modules;

The laser emitting unit in the ONU optical module includes a CML laser and a driving circuit thereof; the driving circuit of the laser emitting unit is configured to receive an electrical signal sent by the ONU system device, and drive the CML laser to emit according to the received electrical signal. Optical signals of a specific wavelength; different wavelengths of optical signals emitted by different ONU optical modules;

The optical signal transmitted by each ONU optical module is coupled to the optical fiber via the first WDM, and transmitted to the OLT via the optical fiber and the second WDM;

For the optical signals of different wavelengths emitted by the ONU optical module, the OLT includes a plurality of laser receiving units for receiving optical signals of each wavelength, and converting the received optical signals into electrical signals and transmitting the signals to the switch.

Preferably, the wavelength of the optical signal emitted by the ONU optical module is located in the C-band or the L-band; and the minimum frequency interval between the optical signals transmitted by the different ONU optical modules is 50 GHz. The number of the ONU optical modules is m, the wavelengths of the optical signals emitted by the ONU optical modules are different, the number of the laser receiving units in the OLT is m, and the optical network uses the point-to-point method for uplink signal transmission. Where m is a natural number.

Or, the number of the ONU optical modules is f, and the f ONU optical modules transmit g optical signals of different wavelengths;

The OLT includes g laser receiving units respectively receiving optical signals of different wavelengths; the optical network adopts a multi-point to one-point method for uplink signal transmission; Where f is a natural number and g is a natural number less than f and greater than or equal to f/2.

Preferably, the optical network further includes: an arrayed waveguide grating AWG;

The uplink port of the AWG is connected to the first WDM, and the downlink ports of the AWG are respectively connected to one ONU optical module; the optical signals transmitted by the ONU optical modules are sent to the first WDM through the downlink ports of the AWG, A WDM is coupled to the optical fiber and transmitted to the OLT via the optical fiber and the second WDM.

According to another aspect of the present invention, an optical network unit optical module including a laser emitting unit, characterized in that

The laser emitting unit includes a CML laser and a driving circuit thereof; the driving circuit of the laser emitting unit is configured to receive an electrical signal transmitted by the ONU system device, and drive the CML laser to perform laser emission according to the received electrical signal.

Preferably, the bias current supply pin of the driving circuit is connected to the cathode of the laser emitting diode in the CML laser through an inductor; a modulation current of the driving circuit provides a pin through the first resistor and the CML The cathode of the laser emitting diode in the laser is connected.

Another modulation current supply pin of the drive circuit is coupled to the anode of the laser light emitting diode in the CML laser through a second resistor, and the second resistor is matched to the first resistor.

The driving circuit is further configured to monitor a current flowing through the PD tube built in the CML laser, and adjust a bias current output to the CML laser according to the monitored current to ensure that the optical power output of the laser is stable.

Further, the optical module further includes:

And a temperature compensation circuit for adjusting a temperature adjustment voltage outputted to the TEC built in the CML laser according to a change in a resistance of the thermocouple built in the CML laser.

The temperature compensation circuit specifically includes:

a voltage dividing circuit connected in series with a thermocouple built in the CML laser;

a standard voltage output circuit for outputting a standard voltage to the voltage dividing circuit and a thermocouple connected in series therewith;

a voltage comparison circuit having a voltage input terminal connected to a connection point of the voltage dividing circuit and the thermocouple for acquiring a voltage on the voltage dividing circuit, and another voltage input terminal for inputting a reference voltage; The voltage comparison circuit compares the voltages of the two voltage input terminals to obtain a voltage difference between the two, and outputs the voltage difference from the output end thereof;

The voltage regulating circuit has an input end connected to the output end of the voltage comparison circuit, and adjusts the temperature adjustment voltage outputted from the output end according to the voltage difference outputted by the voltage comparison circuit. Further, the optical module further includes:

The central wavelength adjustment circuit is configured to receive a control command, and output a corresponding voltage as the reference voltage to another voltage input end of the voltage comparison circuit according to the received control command.

The circuit board of the optical module is divided into a main board and a sub board;

The CML laser and its driving circuit are disposed on the main board, and the temperature compensation circuit and the central wavelength adjusting circuit are disposed on the sub board;

Alternatively, the temperature compensation circuit specifically includes:

a laser temperature determining unit, configured to measure a resistance or a voltage of a thermocouple built in the CML laser, and calculate a current temperature value of the CML laser according to the measurement result; and according to the calculated current temperature value and the temperature setting value The difference, increasing or decreasing the regulated voltage of the output;

The temperature adjustment voltage output circuit is configured to receive the adjustment voltage output by the laser temperature determination unit 1201, and output a corresponding current as the temperature adjustment voltage according to the received adjustment voltage.

Preferably, the optical module is in the form of an SFP package, and the pin definition is compatible with the pin definition of the existing ONU optical module.

Further, the optical module further includes:

The laser receiving unit is configured to receive the downlink optical signal in the passive optical network, and convert the received optical signal into an electrical signal and send the signal to the ONU system device.

The laser emitting unit in the ONU optical module of the embodiment of the present invention can control the spectral width below 0.2 nm by using a CML laser, and the spectrum of the emitted light is stably clamped at the wavelength point of the ITU-T, which is superior. The spectral characteristics, so that the optical signal emitted by the ONU optical module can achieve a narrow spectral width and a small central wavelength offset; thus, the frequency interval at which different ONU optical modules transmit the upstream optical signal can be smaller, thereby being in the optical network. It can accommodate more uplink channels, thereby increasing the bandwidth of the optical network in the uplink direction. At the same time, the number of ONU optical modules that multiplex the same uplink channel can be reduced, so that the uplink bandwidth of each ONU optical module is also improved.

Further, the ONU optical module of the embodiment of the present invention further adopts a temperature compensation circuit, so that the center wavelength of the laser light emitted by the CML laser is prevented from being greatly affected by the temperature, thereby ensuring the stability of the center wavelength of the emitted laser light.

Further, the ONU optical module of the embodiment of the invention further adopts a central wavelength adjustment circuit, which can adjust the center wavelength of the laser light emitted by the CML laser. Compared with the prior art ONU optical modules that can only transmit specific wavelengths, the ONU optical module with adjustable laser center wavelength has better installation and maintenance convenience, and the manufacturer or the operator does not have to transmit different wavelengths. The ONU optical module performs unified planning, but produces and installs a unified ONU optical module, which is based on site requirements. A laser is adjusted to emit the desired wavelength. This greatly reduces production, installation, maintenance, and management costs. DRAWINGS

1 is a schematic structural diagram of a prior art passive optical network;

2 is a circuit block diagram of an internal structure of a laser emitting unit in an ONU optical module according to an embodiment of the present invention;

3 is a schematic structural diagram of a passive optical network according to an embodiment of the present invention;

4 is a passive optical network for performing signal uplink transmission in a point-to-point manner according to an embodiment of the present invention; FIG. 5 is a passive optical network for performing signal uplink transmission in a multi-point-to-point manner according to an embodiment of the present invention; Schematic diagram of the internal circuit of the CML laser;

7 is a specific circuit diagram of a CML laser and a driving circuit thereof according to an embodiment of the present invention; FIG. 8 is a block diagram of a specific implementation circuit of a temperature compensation circuit according to an embodiment of the present invention; FIG. 9 is a schematic diagram of a temperature compensation circuit according to an embodiment of the present invention; Specific implementation circuit;

10 is a schematic diagram of a pulse modulation wave having a large pulse width at a PWM circuit according to an embodiment of the present invention; FIG. 11 is a schematic diagram of a pulse modulation wave having a smaller pulse width at a PWM circuit according to an embodiment of the present invention; Another specific implementation circuit block diagram of the temperature compensation circuit of the example.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings. However, it should be noted that many of the details set forth in the specification are only intended to provide the reader with a thorough understanding of one or more aspects of the present invention.

"The "module", "system:" used in this application is intended to include a computer-related entity such as, but not limited to, hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a module can be, but is not limited to: a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer.

In the passive optical network of the embodiment of the present invention, different ONU optical modules transmit optical signals of different wavelengths in the uplink direction, that is, the uplink direction uses wavelength division multiplexing to transmit signals, and further narrows the uplink channels. Interval, thereby expanding the capacity of the system's upstream channel to achieve the purpose of increasing the system's upstream bandwidth. To reduce the channel spacing, this can be achieved by reducing the spectral width of the laser or by increasing the stability of the laser center wavelength.

Therefore, in the ONU optical module of the embodiment of the present invention, CML (chirp managed laser, 啁啾Manage the laser) As the laser, the spectrum of the emitted laser is controlled below 0.2 nm, and the center wavelength can be stably locked to the ITU-T grid so that the center wavelength shift is between +/- 0.02 nm. In this way, the channel spacing can be reduced, so that the network system can be expanded, that is, more channels are provided, so as to increase the system bandwidth.

The technical solutions of the embodiments of the present invention are described in detail below with reference to the accompanying drawings. The internal structure circuit block diagram of the laser emitting unit in the ONU optical module of the embodiment of the present invention, as shown in FIG. 2, includes: a CML laser 201 and a driving circuit 202 thereof.

The driving circuit 202 is configured to receive an electrical signal transmitted by the ONU system device, and drive the CML laser 201 to emit a laser (optical signal) of a specific wavelength according to the received electrical signal.

CML (Chirp Managed Laser) lasers can control the spectral width below 0.2 nm and stabilize the spectral spectrum of the emitted light at the ITU-T wavelength grid for better spectral characteristics.

Further, the ONU optical module further includes a laser receiving unit configured to receive the downlink optical signal in the passive optical network, and convert the received optical signal into an electrical signal and send the signal to the ONU system device. The laser receiving unit in the ONU optical module can be a structure commonly used in existing passive optical networks, and is well known to those skilled in the art, and will not be described here.

FIG. 3 is a schematic structural diagram of a passive optical network according to an embodiment of the present invention, including: an optical line termination optical module OLT301, a first wavelength division multiplexer WDM302, a second wavelength division multiplexer WDM303, and an AWG (Arrayed Waveguide Graiing) An arrayed waveguide grating 304, a second AWG 305, and at least one ONU (Optical Network Unit) optical module 305.

The number of ONU optical modules 305 in the passive optical network is multiple; the ONU optical modules in the passive optical network transmit upstream optical signals of different wavelengths. After receiving the electrical signal sent by the ONU system device, the ONU optical module 305 converts to an optical signal (ie, an upstream optical signal) output. Specifically, after receiving the electrical signal transmitted by the ONU system device, the laser transmitting unit of the ONU optical module converts the received electrical signal into a (upstream) optical signal output of a specific wavelength. The optical signal outputted by each ONU optical module is coupled to the optical fiber via the WDM 302. The first WDM 302 and the second WDM 303 are connected through the optical fiber, and the optical signal output by each ONU optical module is sent to the OLT 301 via the optical fiber and the second WDM 303.

For the upstream optical signals of different wavelengths transmitted in the optical fiber, the laser receiving unit for detecting and receiving the wavelength signal is respectively used in the OLT 301, and the received optical signal is converted into an electrical signal and then sent to the switch. In other words, for the optical signals of different wavelengths transmitted by the ONU optical module, the OLT 301 includes a plurality of laser receiving units for receiving (upstream) optical signals of each wavelength, and converting the received optical signals into electrical signals and transmitting the signals. Give the switch. For example, ONU light in a passive optical network There are n kinds of wavelengths (frequency) of the optical signals emitted by the module, and n laser receiving units in the OLT 301 respectively receive n kinds of wavelength (frequency) optical signals (n is a natural number) emitted by the ONU optical modules.

Since the laser emitting unit in the ONU optical module 305 adopts a CML laser, the spectral width can be controlled below 0.2 nm, and the spectrum of the emitted light is stably clamped at the ITU-T wavelength grid, which has better spectral characteristics. Therefore, the optical signal emitted by the ONU optical module 305 can achieve a narrow spectral width and a small central wavelength offset; thus, the frequency interval at which the different ONU optical modules transmit the upstream optical signal can be smaller, even at intervals of 50 GHz. Therefore, more uplink channels can be accommodated in the optical network, and the number of ONU optical modules that multiplex the same uplink channel can be reduced, so that the uplink bandwidth of each ONU optical module can be improved.

Optical Line Terminal Optical Module The laser light emitted by each of the laser emitting units in the OLT 301 is coupled to the optical fiber via the second WDM 303. The first WDM 302 and the second WDM 303 are connected by an optical fiber, and the laser light emitted by each laser emitting unit is transmitted in the optical fiber to reach the second WDM 303.

The AWG 304 is connected to the first WDM 302 through an optical fiber. After the optical signal outputted by the first WDM 302 enters the uplink port of the AWG 304, the AWG 304 outputs optical signals of different wavelengths through different downlink ports. Each downlink port of the AWG 304 is connected to an ONU optical module 305.

For the case where the AWG 304 is disposed in the passive optical network, the optical signals transmitted by the ONU optical modules 305 are sent to the first WDM 302 via the downlink ports of the AWG 304, coupled to the optical fiber via the first WDM 302, and sent to the OLT 301 via the optical fiber and the second WDM 303. .

In addition, the laser light emitted by each laser emitting unit of the OLT 301 in the passive optical network is coupled to the optical fiber via the first WDM 302, and after being transmitted by the optical fiber and splitting the AWG, the output is output from the port outputting the corresponding wavelength laser to the ONU optical module. The laser receiving unit of the ONU optical module converts the received optical signal of a specific wavelength into an electrical signal, and then outputs the converted electrical signal to the ONU system device, and the ONU system device processes the electrical signal. The laser emitting unit and the laser receiving unit in the OLT 301 can adopt a structure commonly used in the existing passive optical network, and are well known to those skilled in the art, and will not be described herein.

The passive optical network of the ONU optical module in the embodiment of the present invention can perform uplink uplink transmission in a point-to-point manner without using the multi-point-to-one transmission method of the prior art, thereby greatly increasing each ONU. The upstream bandwidth of the optical module. Of course, the ONU optical module of the embodiment of the present invention can also be applied to a passive optical network in a multi-point-to-one uplink transmission mode.

Figure 4 shows a passive optical network that uses a point-to-point method for uplink transmission of signals; it includes m ONU optical modules (m is a natural number), and the wavelengths of optical signals emitted by each ONU optical module are different, that is, m The ONU optical module emits m optical signals of different wavelengths; thus, passive light There are m uplink channels in the network. The OLT includes m laser receiving units respectively corresponding to m ONU optical modules, wherein the wavelength of the optical signal received by the laser receiving unit is the same as the wavelength of the optical signal emitted by the corresponding ONU optical module.

Assuming that m is 180, the wavelength (frequency) of the laser (optical signal) emitted from the first optical network unit optical module to the laser emitting unit of the 180th optical network unit optical module is located in the L-band, as shown in Table 1 below:

Table 1

It can be seen from the above table that the optical signals transmitted by different optical network unit optical modules can reach a minimum frequency interval of 50 GHz and a wavelength interval of 0.4 nm, which greatly expands the uplink bandwidth in the optical network, and each optical network unit optical module It is not necessary to multiplex the uplink channel with other optical network unit optical modules. Therefore, the uplink bandwidth of each optical network unit optical module is also greatly improved.

Of course, the wavelength of the optical signal emitted by the ONU optical module can also be located in the L-band.

Figure 5 shows a passive optical network that uses a multi-point-to-point method for uplink signal transmission; including f ONU optical modules (f is a natural number), and f ONU optical modules transmit g optical signals of different wavelengths ( g is a natural number less than f and greater than or equal to f/2). Thus, the passive optical network has g uplink channels, and at most two optical network unit optical modules multiplex one uplink channel. The _g laser receiving units in the OLT respectively receive optical signals of different wavelengths, convert the received optical signals into electrical signals, and send them to the switch for processing. In the passive optical network of FIG. 5, at most two optical network unit optical modules multiplex one uplink channel. Therefore, compared with the prior art, the uplink bandwidth of the optical network unit optical module is greatly improved.

Generally, the above-mentioned laser emitting unit operates in a continuous transmission mode, and the laser transmitting unit in the ONU optical module needs to operate in a burst transmission mode to adapt to a situation in which the user does not continuously transmit uplink data. If a laser emitting unit operating in continuous emission mode is applied in an ONU optical module, then none The method enters the normal working state for a normal transmission of the optical signal in a short period of time. Fig. 6 shows an internal circuit diagram of a CML laser, and 1-9 in Fig. 6 shows an external pin after the CML laser is packaged. As can be seen from Fig. 6, the cathode of the CML laser is output through a resistor (RF) and an inductor (L1) through the fourth pin and the seventh pin, respectively. Usually, the pin for the bias current and modulation current supplied by the driver circuit is connected to the fourth pin. The inventors of the present invention analyzed the circuit of the prior art and found that the connection mode is applied in the continuous transmission mode without problems, but if the application is in the burst transmission mode, the driver circuit is provided when the laser is suddenly emitted. The bias current is consumed in a large amount on the resistor of the 4th pin for a period of time, so that the CML laser cannot be supplied with sufficient BIAS bias current to make the laser work normally.

Based on the above analysis, the laser emitting unit provided by the embodiment of the present invention, as shown in FIG. 7, includes a laser emitting diode for emitting laser light, and a laser detecting diode for detecting laser light. The bias current of the driving circuit provides a pin connection to the cathode of the CML laser (ie, the cathode of the laser emitting diode) through an inductor (L1 in FIG. 7), that is, the bias current of the driving circuit provides the pin and the pin in FIG. The seventh pin is connected; the modulation current supply pin of the driving circuit is connected to the cathode of the CML laser (ie, the cathode of the laser emitting diode) through a resistor (RF in FIG. 7), that is, a modulation current of the driving circuit is provided. The pin is connected to the 4th pin in Figure 6. Since the bias current of the driver is used to move the seventh pin of the laser, the current is modulated by the fourth pin of the laser. The bias current is not consumed by the resistance of the fourth pin, and the modulation current is not affected by the inductor. The blocking action of the AC signal is then applied to the laser to form a modulation.

Further, another modulation current supply pin of the driving circuit is connected to the anode of the CML laser (ie, the anode of the laser emitting diode, the third pin of FIG. 6) through another resistor (R4 in FIG. 7), thus driving The modulation current of the circuit output forms a loop through the third pin and the fourth pin in FIG. 6, and the resistor (R4) connected to the third pin can be used to match the resistance (RF) connected to the fourth pin. Thereby the laser works normally in burst mode.

Further, the driving circuit is further configured to monitor a current flowing through a PD (detection diode) tube built in the CML laser, and adjust a bias current output to the CML laser according to the monitored current to ensure that the optical power of the laser output is stable. Specifically, the driving circuit can detect the current flowing through the PD tube through the sixth pin in FIG. 6, and the driving circuit converts the current into a voltage through the built-in resistor, and the converted voltage value drives the circuit to adjust the output bias current; If the converted voltage value is higher than the set voltage value, the output bias current is decreased; if the converted voltage value is lower than the set voltage value, the output bias current is increased; thereby ensuring stable optical power output by the CML laser. The optical power drifts without being affected by temperature or the like. The set voltage value can be set by a person skilled in the art according to the actual situation. Further, the 0NU optical module in the embodiment of the present invention may further include: a temperature compensation circuit 203. The temperature compensation circuit 203 is configured to adjust a temperature adjustment voltage outputted to the TEC built in the CML laser according to a change in the resistance of the thermocouple built in the CML laser; and input a temperature adjustment voltage to the TEC built in the CML laser, Used to adjust the temperature of the CML laser.

Specifically, a resistor can be connected in series with the thermocouple outside the CML laser, and a stable voltage is applied to the thermocouple and the resistor; since the resistance of the thermocouple built in the CML laser generally varies with the temperature in the CML laser. Alternatively, the temperature compensation circuit 203 can know the resistance of the thermocouple by monitoring the voltage across the resistor in series with the thermocouple outside the CML laser, and then understand the temperature inside the CML laser.

The temperature adjustment voltage output from the temperature compensation circuit 203 is input to the TEC (Semiconductor Cooler) built in the CML laser through the first and second pins in Fig. 6. The TEC regulates the temperature of the CML laser based on the voltage difference between pins 1 and 2. Therefore, the temperature compensating circuit 203 can control the temperature in the CML laser by the magnitude, positive and negative of the temperature adjustment voltage input to the CML laser. The temperature point of the CML laser directly affects the center wavelength of the CML laser output laser. In other words, if it is desired that the center wavelength shift of the CML laser output laser is small and stable, it is necessary to control the temperature of the CML laser to be constant. The temperature compensation circuit 203 monitors the temperature in the CML laser by monitoring the change of the resistance of the thermocouple built in the CML laser, and then adjusts the output to the temperature adjustment voltage according to the monitored thermocouple voltage to realize the CML laser. Temperature control keeps the temperature inside the CML laser at a certain temperature.

A block diagram of a specific implementation circuit of the temperature compensation circuit 203 is shown in FIG. 8, and includes: a voltage comparison circuit 801, a voltage adjustment circuit 802, a voltage dividing circuit 803, and a standard voltage output circuit 804. A specific voltage dividing circuit 803 is shown in FIG. 7, and FIG. 9 shows a specific circuit of the voltage comparing circuit 801, the voltage adjusting circuit 802, and the standard voltage output circuit 804.

The voltage dividing circuit 803 is connected in series with the thermocouple built in the CML laser; the voltage dividing circuit 803 may specifically be a resistor, and the resistor R13 of FIG. 7 is the voltage dividing circuit 803: the resistor R13 is connected in series with the thermocouple built in the CML laser, 2.5V The standard voltage is applied to resistor R13 and the thermocouple.

The standard voltage output circuit 804 outputs a standard voltage to the voltage dividing circuit and a thermocouple connected in series therewith. The standard voltage output by the standard voltage output circuit 804, for example, may be 3V, or a DC voltage of 2.3V. The specific voltage value can be set by a person skilled in the art according to actual conditions. The U8 MAX8842 chip in Figure 9 and its peripheral components form the standard voltage output circuit 804. U8 MAX8842 chip is a voltage regulator circuit chip. The 6th pin of the U8 MAX8842 chip outputs a standard voltage of 2.5V and is applied to the voltage dividing circuit 803 and the thermocouple. A voltage input terminal of the voltage comparison circuit 801 is connected to a junction point of the voltage dividing circuit 803 and a thermocouple built in the CML laser, so that a change in voltage on the thermocouple or a change in voltage on the voltage dividing circuit 803 can be monitored. Since the resistance of the thermocouple changes with temperature, the voltage on the thermocouple changes accordingly. Similarly, the voltage on the voltage dividing circuit 803 changes accordingly; that is, the voltage dividing circuit 803 The change in voltage, or the change in voltage across the thermocouple, reflects the change in temperature within the CML laser.

The other voltage input of the voltage comparison circuit 801 is connected to the reference voltage.

The voltage comparison circuit 801 compares the voltages at the two voltage input terminals to obtain a voltage difference between the two, and outputs the voltage difference from its output terminal.

The U7 NCS2001 chip and the U5 NCS2001 chip and its peripheral components in Fig. 9 constitute a voltage comparison circuit 801. Both the U7 NCS2001 chip and the U5 NCS2001 chip are comparator chips. One voltage input terminal of the voltage comparison circuit 801 in FIG. 9 is the voltage input pin 3 of the U7 NCS2001 chip, and the other voltage input terminal of the voltage comparison circuit 801 is the voltage input pin 4 of the U5 NCS2001 chip, and the voltage comparison circuit The output of 801 is the voltage output pin 1 of the U5 NCS2001 chip.

The input end of the voltage regulating circuit 802 is connected to the output end of the voltage comparing circuit 801, and the output end thereof is connected to the TEC built in the CML laser; the voltage adjusting circuit 802 adjusts the output of the output terminal to the TEC according to the voltage difference outputted by the voltage comparing circuit 801. Temperature regulation voltage.

The U6 MAX8521 chip and its peripheral components in Figure 9 form the voltage regulation circuit 802. The U6 MAX8521 chip is a voltage-controlled PWM chip. The input terminal of the voltage regulating circuit 802 is the pin 10 of the U6 MAX8521 chip. As can be seen from FIG. 9, the input terminal of the voltage regulating circuit 802, that is, the pin 10 of the U6 MAX8521 chip and the voltage output pin 1 of the U5 NCS2001 chip. Connected, the U6 MAX8521 chip performs pulse width modulation of the PWM wave according to the voltage output by the voltage comparison circuit 801, and the modulated PWM wave is output from the pins 18 and 19 of the U6 MAX8521 chip; and the pins 18 and 19 of the U6 MAX8521 chip respectively Connected to the TEC- (the 1st pin in Figure 6) and TEC+ (the 2nd pin in Figure 6) of the CML laser to output the modulated PWM (Pulse-Width Modulation) wave to the CML The TEC of the laser.

For example, when it is required to raise the temperature of the CML laser, the voltage regulating circuit 802 outputs a pulse modulated wave having a relatively large positive pulse width, as shown in FIG. 10;

When it is required to cool the CML laser, the voltage regulating circuit 802 outputs a pulse modulated wave having a small positive pulse width and a large negative pulse width, as shown in FIG.

Further, the ONU optical module in the embodiment of the present invention may further include: a central wavelength adjustment circuit 204.

The central wavelength adjustment circuit 204 is configured to receive a control command, and output a corresponding voltage according to the received control command as a reference voltage of the other voltage input terminal of the access voltage comparison circuit 801. That is, the center wavelength adjustment circuit 204 outputs a corresponding reference voltage based on the received control command.

The central wavelength adjustment circuit 204 may specifically include a single chip microcomputer, a micro controller, a processor, and the like. The central wavelength adjustment circuit 204 may specifically receive a control command through a communication port, such as a serial communication port USB, RS232, or a switch that is detected by a pin. Status to receive and obtain control commands set by the engineer.

In fact, the reference voltage output by the central wavelength adjustment circuit 204 has a corresponding relationship with the wavelength of the laser light emitted by the CML laser; the relationship between the reference voltage output by the central wavelength adjustment circuit 204 and the wavelength of the laser light emitted by the CML laser, Personnel can be based on experience or experimentation. For example, the correspondence obtained according to experience or experiment is: if the reference voltage outputted by the central wavelength adjustment circuit 204 is increased in the case where the temperature does not change, the voltage comparison circuit 801 obtains between the two voltage input terminals. The voltage difference is reduced, so that the PWM circuit 802 reduces the pulse width of the pulse modulation current, resulting in a decrease in the temperature adjustment voltage of the input CML laser, and the wavelength of the laser light emitted by the CML laser becomes longer;

In the case where the temperature does not change, if the reference voltage output from the center wavelength adjustment circuit 204 decreases, the voltage difference between the two voltage input terminals obtained by the voltage comparison circuit 801 increases, so that the PWM circuit 802 increases the pulse. The pulse width of the modulation current causes the temperature adjustment voltage of the input CML laser to increase, and the wavelength of the laser light emitted by the CML laser becomes shorter.

After obtaining the relationship between the reference voltage outputted by the central wavelength adjustment circuit 204 and the wavelength of the laser light emitted by the CML laser, the technician presets the reference voltage corresponding to the wavelength of the laser light emitted by the CML laser to the central wavelength adjustment circuit 204. . When the control command received by the center wavelength adjustment circuit 204 indicates that a laser of a certain wavelength is output, the center wavelength adjustment circuit 204 outputs a reference voltage corresponding to the wavelength. For example, if the control command received by the central wavelength adjustment circuit 204 indicates that the laser light of the A wavelength is output, the central wavelength adjustment circuit 204 outputs the reference voltage A; the control command received by the central wavelength adjustment circuit 204 indicates that the laser light of the B wavelength is output, and the central wavelength adjustment circuit 204 Output reference voltage B. The central wavelength adjustment circuit 204 can realize the CML laser to emit laser light of different center wavelengths by outputting different reference voltage values. For example, the central wavelength adjustment circuit 204 can control the ONU optical module to emit nine different wavelengths of laser light (optical signals) by outputting nine different reference voltage values.

A block diagram of another specific implementation circuit of the temperature compensation circuit 203 is shown in FIG. 12, including: The illuminator temperature determining unit 1201 and the temperature adjusting voltage output circuit 1202.

The laser temperature determining unit 1201 may specifically be a single-chip microcomputer having a thermocouple resistance measuring function, a processor, or a single-chip microcomputer having a voltage measuring function and a processor. The laser temperature determining unit 1201 measures the resistance or voltage of the thermocouple built in the CML laser, calculates the current temperature value of the CML laser according to the measurement result, and increases or decreases according to the difference between the calculated current temperature value and the temperature set value. Small output regulation voltage. The temperature setting value therein is set by a person skilled in the art according to the actual situation.

The temperature adjustment voltage output circuit 1202 receives the adjustment voltage output from the laser temperature determination unit 1201, and outputs a corresponding voltage as a temperature adjustment voltage to the CML laser in accordance with the received adjustment voltage. The temperature adjustment voltage output circuit 1202 may specifically be a voltage controlled PWM circuit.

The circuit board of the ONU optical module of the embodiment of the present invention is divided into a main board and a sub board; the CML laser and its driving circuit are disposed on the main board, and the temperature compensation circuit and the center wavelength adjusting circuit are disposed on the sub board. In order to avoid the temperature compensation circuit and the central wavelength adjustment circuit to introduce interference to the CML laser and its drive circuit.

Further, the ONU optical module of the embodiment of the present invention further adopts a central wavelength adjustment circuit, which can adjust the center wavelength of the laser light emitted by the CML laser. Compared with the prior art ONU optical modules that can only transmit specific wavelengths, the ONU optical module with adjustable laser center wavelength has better installation and maintenance convenience, and the manufacturer or the operator does not have to transmit different wavelengths. The ONU optical module performs unified planning, but produces and installs a unified ONU optical module, which is adjusted according to field requirements to emit laser light of the desired wavelength. This greatly reduces production, installation, maintenance, and management costs.

One of ordinary skill in the art can understand all or part of the steps in the method of implementing the above embodiments. It can be completed by a program to instruct related hardware, and the program can be stored in a computer readable storage medium, such as: ROM/RAM, disk, optical disk, and the like.

The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It is considered as the scope of protection of the present invention.

Claims

Claim

A passive optical network, comprising: an optical line terminal optical module OLT, a first wavelength division multiplexer WDM, a second wavelength division multiplexer WDM, and a plurality of ONU optical modules;

The optical network according to claim 1, wherein the wavelength of the optical signal emitted by the ONU optical module is located in a C band or an L band;

The minimum frequency interval between the optical signals emitted by different ONU optical modules is 50 GHz.

The optical network according to claim 1, wherein the number of the ONU optical modules is m, and the wavelengths of the optical signals emitted by the ONU optical modules are different, and the laser receiving units in the OLT are different. The number is m; and the optical network performs signal uplink transmission in a point-to-point manner; wherein m is a natural number.

The optical network according to claim 1, wherein the number of the ONU optical modules is f, and the fth ONU optical modules transmit optical signals of different wavelengths;

The OLT includes g laser receiving units respectively receiving g optical signals of different wavelengths; the optical network adopts a multi-point to one-point method for uplink signal transmission;

Where f is a natural number and g is a natural number less than f and greater than or equal to f/2.

5. The optical network of any of claims 1-4, further comprising: an arrayed waveguide grating 'AWG;

The uplink port of the AWG is connected to the first WDM, and the downlink ports of the AWG are respectively connected to one ONU optical module; the optical signals emitted by the ONU optical modules are respectively downlinked through the AWG. The port is sent to the first WDM, coupled to the optical fiber via the first WDM, and sent to the OLT via the optical fiber and the second WDM.

An optical network unit optical module, comprising a laser emitting unit, wherein the laser emitting unit comprises a CML laser and a driving circuit thereof; and the driving circuit of the laser emitting unit is configured to receive the sending by the ONU system device An electrical signal that drives the CML laser for laser emission based on the received electrical signal.

7. The optical module of claim 6, wherein

a bias current supply pin of the driving circuit is coupled to a cathode of a laser emitting diode in the CML laser through an inductor; a modulation current of the driving circuit provides a pin through the first resistor and a laser in the CML laser The cathode of the emitting diode is connected.

8. The optical module of claim 7, wherein

9. The light module of claim 8 wherein:

10. The optical module of claim 6, further comprising:

The optical module according to claim 10, wherein the temperature compensation circuit comprises:

a voltage comparison circuit having a voltage input terminal connected to the voltage dividing circuit and the thermocouple The contacts are connected to obtain the voltage on the divided piezoelectric circuit, and the other voltage input terminal is connected to the reference voltage; the voltage comparison circuit compares the voltages of the two voltage input terminals to obtain a voltage difference between the two, and the voltage difference is obtained from the voltage difference Output output

And a voltage regulating circuit, wherein an input end thereof is connected to an output end of the voltage comparison circuit, and the temperature adjustment voltage outputted from the output end thereof is adjusted according to a voltage difference outputted by the voltage comparison circuit.

12. The optical module of claim 11, further comprising:

The optical module according to claim 12, wherein the circuit board is divided into a main board and a sub board;

The optical module of claim 10, wherein the temperature compensation circuit comprises:

The optical module according to any one of claims 6-14, wherein the optical module is in the form of an SFP package, and the pin definition is compatible with the pin definition of the existing ONU optical module.

The optical module according to any one of claims 6 to 14, further comprising: a laser receiving unit, configured to receive a downlink optical signal in the passive optical network, and convert the received optical signal into an electrical signal Send to the ONU system device.