CN111323879A - Optical module - Google Patents

Abstract

The laser chip in the optical module involved in the present invention includes a substrate and a waveguide integrated on the upper surface of the substrate. The upper surface of the substrate is further provided with a heating unit for temperature compensation of the waveguide, and the heating unit is close to the waveguide. The upper surface of the substrate of the chip is provided with a heating unit for temperature compensation of the waveguide, which realizes direct heat transfer between the heating unit and the waveguide, avoids heat loss, greatly improves heating efficiency, and reduces power consumption. In this way, it is easy to tune the center wavelength of the laser chip within the industrial temperature range, and obtain an optical module that meets the wavelength range of 5G fronthaul MWDM, which broadens the wavelength range of the laser chip, reduces the power consumption of the optical module, and improves the laser chip. The yield can be achieved for 5G fronthaul application scenarios, so that expensive TECs are no longer used for temperature tuning, which saves the material cost of 5G fronthaul optical modules.

Description

Optical module

technical field

The invention relates to an optical module and belongs to the technical field of optical communication.

Background technique

For optical fiber communication systems, in order to make full use of the advantages of optical fibers in transmission capacity, it is necessary to build a wavelength division multiplexing system. According to the traditional division method, the optical fiber transmission bandwidth can be divided into sparse wavelength division multiplexing CWDM (Coarse Wavelength Division Multiplexing) according to the grid. ) interval, dense wavelength division multiplexing interval, Lan-WDM multiplexing interval. With the construction of the 5G system, a new division method of the wavelength division network is proposed, which is called the Open-WDM/MWDM scheme. The operating wavelength of the laser chip has a certain drift with the temperature change, and the drift coefficient is about 0.1nm/℃. At the working temperature, the laser wavelength drift range is about 9.5nm in the full temperature range. In order to ensure the crosstalk control between channels, for the CWDM multiplexing mode, the wavelength offset range is required to be no more than 6.5nm. For other multiplexing systems, the offset control is more stringent. The traditional technical solution is to use a thermoelectric cooler TEC (Thermal Electric Cooler) to control the working environment temperature of the laser, but because the TEC needs a dedicated chip to control it, and the TEC is in the working state of heating and cooling, with the temperature control range. Increase, the efficiency will decrease, resulting in a large amount of invalid power loss. With the limitation of module power consumption, it often cannot meet the actual module usage requirements. The 5G optical fiber transmission network has strict requirements on the cost and power consumption of the optical module. At present, in order to work in an industrial temperature environment (-40°C-85°C), a heating sheet is mounted outside the laser, or a heating resistance wire is wound. , the heat is transferred to the internal laser through thermal conduction, but this method has low thermal conduction efficiency and large power consumption, and also increases the size of the device. In addition, the laser and heater are placed on the thermal isolation substrate. Although this method has a good heating effect at low temperature, the thermal isolation substrate will hinder the heat dissipation of the die, which reduces the working ability of the component to adapt to the high temperature environment. Another method is to set the heater on the carrier close to the laser chip. However, the carrier connected to the laser chip needs to be heated together. The volume of the carrier is much larger than that of the laser. Most of the heat in the heating state is used for heating the carrier. , resulting in low efficiency.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an optical module that can effectively adjust the emission wavelength to meet the wavelength range of 5G fronthaul MWDM.

In order to achieve the above object, the present invention provides the following technical solutions: an optical module, comprising a housing, a light emitting component disposed in the housing, and a circuit board connected to the light emitting component, the light emitting component comprising: A laser chip, the laser chip includes a substrate and a waveguide integrated on the upper surface of the substrate, the upper surface of the substrate is further provided with a heating unit for temperature compensation of the waveguide, and the heating unit is close to the the waveguide.

Further, the distance between the heating unit and the waveguide is 10um˜100um.

Further, the heating unit is fixed on the upper surface of the substrate by thermally conductive glue.

Further, the heating unit is completely fixed on the upper surface of the substrate.

Further, the heating unit is partially fixed on the upper surface of the substrate.

Further, the optical module includes a substrate, the laser chip is disposed on the substrate, and a heat insulating unit for heat insulation is disposed between the heating unit and the substrate.

Further, the heating unit is a thermal resistor formed of Ti metal.

Further, the resistance value of the heating unit is determined by the following formula:

R=ρ*L/S

Among them, R is the resistance value of the heating unit; ρ represents the resistivity of the heating unit; L is the length of the heating unit; S is the cross-sectional area of the heating unit perpendicular to the current direction.

Further, the optical module further includes a temperature sensor for detecting temperature and a temperature control unit signally connected to the temperature sensor and the heating unit, and the temperature control unit is based on the temperature value detected by the temperature sensor. The heating unit is controlled to be turned on or off.

Further, the temperature compensation control method for the optical module includes:

The temperature sensor collects the current temperature value;

Based on the temperature value collected by the temperature sensor, the temperature control unit determines whether the temperature value is lower than a preset temperature threshold;

If the temperature is lower than the preset temperature threshold, the heating unit is controlled to start.

The beneficial effects of the present invention are: the present invention realizes the direct heat transfer between the heating unit and the waveguide by arranging the heating unit for temperature compensation of the waveguide at the position of the upper surface of the substrate of the laser chip close to the waveguide, thereby avoiding the heat transfer. loss, greatly improve heating efficiency and reduce power consumption, so as to easily tune the center wavelength of the laser chip within the industrial temperature range, and obtain an optical module that meets the wavelength range of 5G fronthaul MWDM, which broadens the wavelength range of the laser chip and reduces the The power consumption level of the optical module improves the yield rate of the laser chip, which can realize the 5G fronthaul application scenario, so that the expensive TEC is no longer used for temperature tuning, which saves the material cost of the 5G fronthaul optical module.

The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, and implement it according to the content of the description, the preferred embodiments of the present invention are described in detail below with the accompanying drawings.

Description of drawings

FIG. 1 is a partial structural schematic diagram of an optical module provided with a heating unit according to the first embodiment of the present invention;

2 is a partial structural schematic diagram of an optical module provided with a heating unit according to a second embodiment of the present invention;

3 is a partial structural schematic diagram of an optical module provided with a heating unit according to a third embodiment of the present invention;

FIG. 4 is a schematic structural diagram of the heating unit shown in FIG. 3;

FIG. 5 is a schematic structural diagram of the heating unit shown in FIG. 3 in another direction;

FIG. 6 is a partial structural schematic diagram of an optical module provided with a heating unit according to a fourth embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated mechanism or element must have a specific orientation or a specific orientation. construction and operation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first", "second", and "third" are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

An optical module shown in an embodiment of the present invention includes a housing, a light-receiving component disposed in the housing, a light-emitting component, a circuit board connected to the light-receiving component and the light-emitting component, and a light-receiving component disposed on the housing and connected to the light-receiving component An interface unit that is signal-connected with the light emitting component for sending or receiving electrical signals, wherein the light receiving component is used to convert the received optical signal into an electrical signal and output to the interface unit; the light emitting module is used to transmit the electrical signal sent by the interface unit. Converted to optical signal output. The optical module also includes a control unit that is signally connected to the interface unit, the light receiving component, and the light emitting component, and a power supply unit that provides power for the interface unit, the light receiving component, and the light emitting component and controls the opening and closing of each component. The control unit Used to control the optical module through the internal communication interface. The structure of the optical module is the existing structure, and the preparation method of the optical module is the existing technology, which will not be repeated here.

The light emitting component includes a laser chip, and the laser chip includes a substrate and a waveguide integrated on the upper surface of the substrate. In this embodiment, the laser chip is a DFB laser chip, and the DFB laser chip is a ridge waveguide structure. Of course, in other implementations In an example, the laser chip may also be other types of chips, which are not specifically limited here. Wherein, the substrate may be a SiC substrate, but is not limited thereto, and may also be other substrates. The cross section of the laser chip from bottom to top includes an indium phosphide (InP) substrate, a buffer growth layer, a lower confinement layer, a lower waveguide layer, an active layer (Multi Quantum Well), an upper confinement layer, an upper waveguide layer, and a phosphating layer. Indium (InP) spacer layer and ohmic contact layer. The structure of the DFB laser chip is the existing structure, and the preparation method of the DFB laser chip is the prior art, which will not be repeated here.

In order to tune the center wavelength of the laser chip within the industrial temperature range (-40°C-85°C) and obtain an optical module that meets the wavelength range of 5G fronthaul MWDM, a single temperature control technology can be used. The laser is heated to increase the operating temperature, thereby reducing the operating temperature range of the laser, thereby reducing the difficulty of the control circuit. Or by optimizing the heat conduction method, the heating efficiency can be improved and the power consumption can be reduced. In this embodiment, the upper surface of the substrate is provided with a heating unit for temperature compensation of the waveguide, the heating unit is close to the waveguide, and the distance between the heating unit and the waveguide is 10um to 100um. Setup is required. For the Oclaro HL13BFCP00 series chips, the distance between the heating unit and the waveguide is 20um~50um. Similarly, for the 1xxD-25GLxx11-xxx and 1xxx-25B-Lxx11-S3 series in the Macom 25G DFB chips, the distance between the heating unit and the waveguide is The distance is 20um ~ 50um.

It should be noted here that due to the large area of the upper surface of the substrate, the heating unit is arranged on the upper surface of the substrate. When the heating unit is arranged close to the waveguide, the contact area between the heating unit and the substrate is large enough to avoid This improves the heating rate of the heating unit to the substrate near the location of the waveguide, and avoids the heat passing through one or more heat sinks and through multiple carriers of different thicknesses to directly heat the location of the waveguide, which greatly improves the heating efficiency. , reducing power consumption. Of course, the number of heating units provided may be multiple, and the plurality of heating units are provided at positions close to the waveguide.

Specifically, the heating unit is fixed on the upper surface of the substrate through thermal conductive glue, so that the heating unit overlaps with the upper surface of the substrate as much as possible, thereby improving the heating efficiency of the waveguide, wherein the heating unit can be completely fixed on the substrate The heating unit can also be partially fixed on the upper surface of the substrate. Certainly, in other embodiments, the heating unit may also be fixed on the upper surface of the substrate by using other materials or methods, which is not limited herein.

Referring to FIG. 1, the optical module shown in the first embodiment of the present invention includes a substrate 11, and a metal electrode 111 is disposed on the substrate 11. The metal electrode 111 includes a positive electrode and a negative electrode. The specific locations of the positive electrode and the negative electrode are different from The specific shape is not specifically limited here, and can be set and prepared according to actual needs. It is true that in other embodiments, the electrodes can also be made of other materials, which are not listed here. In addition, the collective material of the substrate 11 and the The shape and the like are not specifically limited here. The substrate 11 is a ceramic sheet, but the substrate 11 is not specifically limited. In other embodiments, the substrate 11 may also be made of other materials. The laser chip 12 with the substrate 121 is disposed on the substrate 11. In this embodiment, the laser chip 12 is fixed on the substrate 11 by welding, and the heating unit 13 is fixed on the upper surface of the substrate 121 by thermally conductive glue. In the embodiment, the fixing manners of the laser chip 12 and the heating unit 13 may also be other manners, which are not specifically limited herein.

In this embodiment, the heating unit 13 includes a thermal resistor 131 formed of Ti metal. Ti meets the requirements of high resistivity and low cost at the same time. The thermal resistor 131 is arranged on the surface of the heating substrate 132, wherein the heating substrate 132 is The rectangular parallelepiped structure, the thermal resistance 131 is arranged on the upper surface of the heating substrate 132, and the two ends of the thermal resistance 131 are provided with wire bonding pad electrodes 133, one as the positive electrode and the other as the negative electrode, which is bonded with the ceramic by gold wire. The metal electrodes 111 on the substrate 11 are connected, and then a current can be introduced to the thermal resistance 131 through TO pins or Box gold fingers to realize the heating function. In other embodiments, the heating substrate can be any other desired shape, the thermal resistance can also be other metal materials or other materials with higher resistivity, and the heating unit can also be any other device or material that can generate thermal energy , the heating unit may also have other structures, shapes or forms, which will not be exemplified here.

The length, width and thickness of the thermal resistor 131 are determined by the required resistance value. Specifically, the resistance value of the thermal resistor 131 is determined by the following formula:

R=ρ*L/S

Wherein, R is the resistance value of the heating unit 13; ρ represents the resistivity of the heating unit 13; L is the length of the heating unit 13; S is the cross-sectional area of the heating unit 13 perpendicular to the current direction.

In this embodiment, the thermal resistance 131 is in the shape of an elongated strip and is arranged in an S-like shape. In this way, the space can be used to the greatest extent possible, so that the heating efficiency of the thermal resistance 131 can be maximized, and the resistance value of the thermal resistance 131 is based on the actual It needs to be set, but it needs to meet the power consumption of about 500mW when passing a current of 100mA, and the thermal resistor 131 can heat the DFB laser so that the wavelength tuning range generated by the DFB laser is about 5nm. Certainly, in other embodiments, the shape of the thermal resistance may also be other, and the shape of the thermal resistance is not specifically limited here, and may be determined according to the actual situation.

The laser chip 12 in this embodiment is large enough, and the heating units 13 can all be fixed on the upper surface of the substrate 121 and close to the waveguide 122 arranged in the middle of the substrate 121, so as to achieve as much heat generated by the heating resistor 131 as possible. Used to heat the waveguide 122 . The substrate 121 of the laser chip 12 is provided with two wire bonding pad electrodes 123, one as the positive electrode and the other as the negative electrode, which are connected to the corresponding metal electrodes 111 on the ceramic substrate 11 in the form of gold wire bonding, and then can be TO pins or Box gold fingers introduce current.

This heating method can be applied to packaging methods such as TO packaging or BOX packaging, and it is only necessary to fix the heating unit 13 on the upper surface of the substrate 121 by means of a thermally conductive adhesive during the preparation process.

Referring to FIG. 2 , the structure of the optical module shown in the second embodiment of the present invention is basically the same as the structure of the optical module shown in the first embodiment, the difference is that the laser chip 22 is relatively small, at this time, the heating unit 23 can be Part of the heating unit 23 is fixed on the upper surface of the substrate 221, and the other part of the heating unit 23 extends beyond the laser chip 22. An insulating unit 24 is provided between the heating unit 23 and the substrate 21 for heat insulation. The insulating unit 24 can be an insulating gasket 24. On the one hand, 24 insulates the heat transfer from the heating unit 23 to the substrate 221 , and on the other hand, is used to support the heating unit 23 , so that the heating unit 23 is fixed on the upper surface of the substrate 221 and the substrate 221 can be stably and continuously adhered. Two ends of the heat insulating unit 24 can be fixed on the heating unit 23 and the base plate 21 respectively by glue with poor thermal conductivity, and the size of the heat insulating unit 24 can be further set according to actual needs. In other embodiments, the material and shape of the heat insulating unit 24 and the fixing manner of the heating unit 23 and the substrate 21 may be other, which are not specifically limited herein. In this embodiment, in order to make the thermal resistor 231 adhere to the substrate 221 as much as possible, two wire bonding pad electrodes 233 are arranged side by side on the part beyond the laser chip 22 to further improve the heat transfer efficiency.

Referring to FIGS. 3 to 5 , the structure of the optical module shown in the third embodiment of the present invention is basically the same as that of the optical module shown in the first embodiment. The difference is that the thermal resistance 331 of the heating unit 33 can be covered with One surface of the heating substrate 332 is heated, an electrode film 334 is respectively provided at both ends of the heating substrate 332, and the two electrode films 334 extend to the other surface of the heating substrate 332, on the other surface of the heating substrate 332 Pads 333 are arranged on the two electrode films 334 on the surface, and the side covered with the thermal resistors 331 is attached to the substrate 321 to further improve the heating efficiency, or the size of the heating unit 33 can be reduced, so that the heating The unit 33 can heat the laser chip 32 of smaller size. In this embodiment, the shape and material of the electrode film 334 are not limited.

Referring to FIG. 6 , the structure of the optical module shown in the fourth embodiment of the present invention is basically the same as that of the optical module shown in the third embodiment. The difference is that the laser chip 42 is relatively small, and the heating unit 43 is partially fixed on the On the upper surface of the substrate 421, the other part of the heating unit 43 extends beyond the laser chip 42. An insulating unit 44 for heat insulation is provided between the heating unit 43 and the substrate 41. The specific insulating unit 44 is the same as the insulating unit 24 shown in the second embodiment. are exactly the same, and will not be repeated here.

Indeed, in other embodiments, in order to satisfy the wavelength tuning of the central wavelength of the DFB laser chip within the industrial temperature range, the upper and lower surfaces of the heating substrate of the heating unit may be provided with thermal resistors. The specific method is the same as that of the first embodiment or the third embodiment. The embodiments are the same, and are not repeated here.

In this application, the heating unit is directly bonded to the surface of the laser chip. Compared with the TEC temperature control method, the heating unit is closer to the waveguide of the laser chip, and the lower part of the waveguide is the position where the active area of the laser chip emits light. Therefore, The short distance is conducive to faster heat transfer to the active area, faster temperature transfer, higher heat transfer efficiency, and easier wavelength tuning. Therefore, a larger wavelength tuning range can be achieved with less electrical power, reducing the need for optical modules. power consumption level.

The TEC in the optical module is omitted. By rationally designing the power wavelength tuning target when the heating unit is working, a temperature compensation range far greater than that of the TEC temperature control can be achieved to meet the center wavelength deviation required by the 5G fronthaul MWDM solution within the range of ±2.5nm , leave a margin of ±1.5nm for the wavelength selection of the laser chip, and relax the wavelength selection requirements of the laser chip, thereby relaxing the difficulty of selecting the wavelength of the laser chip after the single wafer tape-out, and improving the wave yield rate of the laser chip , reduce the material cost of the optical module. Specifically, the material cost of the 5G fronthaul optical module can be reduced by about 20%. The increase in yield means that the number of qualified chips produced by a single wafer will be more, and the price of the chip will be reduced, which also indirectly reduces the cost of the optical module. The methods involved in this application are still applicable to 6G, 7G, etc. that appear in the future.

The optical module further includes a temperature sensor for detecting temperature, and a temperature control unit signally connected to the temperature sensor and the heating unit. The temperature control unit controls the heating unit to start or shut down according to the temperature value detected by the temperature sensor. When it is easy to think of, the temperature detected by the temperature sensor can be the temperature of components such as laser chips. In this application, there is no restriction on the specific position of the temperature sensor in the optical module, and the temperature sensor is set at the corresponding position according to actual needs. , and the type of the temperature sensor is not limited, it can be a thermocouple and other types, which are not listed here.

Temperature compensation control methods for optical modules include:

The temperature sensor collects the current temperature value;

Based on the temperature value collected by the temperature sensor, the temperature control unit determines whether the temperature value is lower than the preset temperature threshold;

If it is lower than the preset temperature threshold, control the heating unit to start.

When the temperature value is higher than the preset temperature threshold, the heating unit is controlled to be turned off.

The specific preset temperature threshold can be set according to the actual situation, and the specific temperature compensation control method is in the prior art, which will not be repeated here. It should be noted here that the temperature control unit includes at least one logic control circuit, and the at least one logic control circuit realizes the determination between the temperature value and the preset temperature threshold value, and controls the heating unit to start or shut down.

Regarding the acquisition of the temperature of the optical module, in other embodiments, a temperature sensor may not be provided in the optical module, but a wavelength detection device is used to detect the wavelength of the laser chip, and the corresponding temperature is calculated according to the wavelength, thereby controlling the activation of the heating unit or off, the wavelength detection device is not specifically limited here, and can be any device capable of detecting wavelengths. It should be noted that the acquisition of the temperature of the optical module may also be in other manners, which are not listed one by one here.

To sum up, in the present invention, a heating unit for compensating the temperature of the waveguide is provided on the upper surface of the substrate of the laser chip near the waveguide, so as to realize the direct heat transfer between the heating unit and the waveguide, avoid the loss of heat, and greatly reduce the loss of heat. Improve heating efficiency and reduce power consumption, so as to easily tune the center wavelength of the laser chip within the industrial temperature range, and obtain an optical module that meets the wavelength range of 5G fronthaul MWDM, which broadens the wavelength range of the laser chip and reduces the power of the optical module. This reduces the power consumption level, improves the yield of laser chips, and can be used in 5G fronthaul application scenarios, so that expensive TECs are no longer used for temperature tuning, which saves the material cost of 5G fronthaul optical modules.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (10)

1. An optical module is characterized by comprising a shell, an optical transmission assembly arranged in the shell and a circuit board connected with the optical transmission assembly, wherein the optical transmission assembly comprises a laser chip, the laser chip comprises a substrate and a waveguide integrated on the upper surface of the substrate, the upper surface of the substrate is also provided with a heating unit for performing temperature compensation on the waveguide, and the heating unit is close to the waveguide.

2. The optical module of claim 1, wherein a distance between the heating unit and the waveguide is 10um to 100 um.

3. The optical module as claimed in claim 1, wherein the heating unit is fixed to the upper surface of the substrate by a thermally conductive adhesive.

4. A light module as claimed in claim 3, characterized in that the heating unit is completely fixed to the upper substrate surface.

5. A light module as claimed in claim 3, characterized in that the heating unit part is fixed to the substrate upper surface.

6. The optical module according to claim 5, wherein the optical module includes a substrate on which the laser chip is disposed, and a heat insulating unit for insulating heat is disposed between the heating unit and the substrate.

7. The optical module according to claim 7, wherein the heating unit is a thermal resistor formed of Ti metal.

8. A light module as claimed in claim 1, characterized in that the resistance value of the heating element is determined by the formula:

R＝ρ*L/S

wherein R is the resistance value of the heating unit; ρ represents the resistivity of the heating element; l is the length of the heating unit; s is the cross-sectional area of the heating unit perpendicular to the current direction.

9. The light module as claimed in claim 1, further comprising a temperature sensor for detecting a temperature and a temperature control unit in signal connection with the temperature sensor and the heating unit, wherein the temperature control unit controls the heating unit to be turned on or off according to a temperature value detected by the temperature sensor.

10. The optical module according to claim 9, wherein a temperature compensation control method for the optical module comprises:

the temperature sensor collects a current temperature value;

based on the temperature value acquired by the temperature sensor, the temperature control unit judges whether the temperature value is lower than a preset temperature threshold value;

and if the temperature is lower than the preset temperature threshold value, controlling the heating unit to start.

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