Method for Controlling Optical Device

Abstract

The present invention relates to a wavelength-tunable optical device in which a semiconductor laser diode chip equipped with a heater or a wavelength-selective filter equipped with a heater is in thermal contact with a thermoelectric element, the thermoelectric element is fixed at a constant temperature, and the channel is varied by varying the average power applied to the heater. The invention provides a method for stopping the operation of the heater even if a malfunction occurs in the heater, or for operating the heater regardless of the channel setting, and for varying the channel by changing the temperature of the thermoelectric element.

Description

Technology Field

[0001] The present invention relates to a driving method for a wavelength-tunable optical device that varies the wavelength transmitted or received. Background Technology

[0002] The communication method currently being standardized under the name NG-PON2 adopts the TWDM (time wavelength division multiplexing) method. The TWDM method refers to a method of sharing an optical fiber in which multiple subscribers simultaneously connected to a single optical fiber can arbitrarily select one of four or eight allowed wavelength channels, and multiple subscribers using the same wavelength channel exchange time only at predetermined times using the TDM (time division multiplexing) method.

[0003] In the TWDM method, four or eight different wavelengths are used simultaneously, and the frequency spacing between these channels is set to 100 GHz. Wavelength tuning methods for transmitting optical devices include changing the temperature of a semiconductor laser and changing the resonant wavelength of an external resonator in an external resonator type laser structure. A wavelength-tunable photodetector is created by placing a wavelength-selective filter that changes the transmitted wavelength according to temperature, and by changing the temperature of this wavelength-tunable filter to vary and select the transmitted wavelength.

[0004] In other words, even in the case of a laser used as a light-emitting element, the emission wavelength can be varied by changing the laser temperature, and the received wavelength can be changed by changing the temperature of the wavelength-selective filter of the photodetector. Changing the temperature of a semiconductor laser or a photodetector filter involves making thermal contact with a thermoelectric cooler and then adjusting the temperature of the thermoelectric cooler to control the transmitted wavelength of the semiconductor laser or photodetector filter. However, as shown in Fig. 1, the thermoelectric cooler has a very slow operating speed of about 0.2 to 0.3 seconds.

[0005] The NG-PON2 standard (ITU-T G.989.3), which is currently being standardized internationally, divides the transmission and reception channel switching time between channels with a wavelength interval of 100 GHz into a standard of 1 sec (class 3) and a standard of 25 msec (class 2), and their uses differ.

[0006] Currently, for Class 3, some companies achieve wavelength tuning by temperature-regulating the transmitting semiconductor laser and the receiving optical selective filter using thermoelectric elements, while for Class 2, they use a method in which heaters are mounted on the semiconductor laser and the wavelength selective filter of the photodetector, placed on a thermoelectric element maintained at a constant temperature, and then driven to select the channel. The problem to be solved

[0007] In these existing methods, Class 2 wavelength tuning utilizes a method where the channel is varied based on the heat generated by a heater mounted on a semiconductor laser diode and a heater mounted on the optical selection filter of a photodetector; however, if a malfunction occurs in the heater during operation, channel tuning does not take place, resulting in a problem where smooth communication cannot be performed.

[0008] The present invention provides a method that enables channel variation even when a problem occurs in a semiconductor laser operating in class 2 and a heater mounted on a wavelength-selective filter of a photodetector. means of solving the problem

[0009] The present invention provides a method that enables channel variation even when a problem occurs in a semiconductor laser operating in class 2 and a heater mounted on a wavelength-selective filter of a photodetector. Effects of the invention

[0010] According to one embodiment of the present invention, the semiconductor laser operating in class 2 and the heater mounted on the wavelength-selective filter of the photodetector have the advantage of enabling channel variation even if a problem occurs. Brief explanation of the drawing

[0011] Figure 1 is a graph showing the rate of temperature reduction by a thermoelectric element. Figure 2 is a diagram illustrating the temperature change of a light-emitting element by a heater mounted on the light-emitting element. Figure 3 is a diagram illustrating a semiconductor laser equipped with a heater placed on a thermoelectric element. Figure 4 is a diagram showing a wavelength-selective filter equipped with a heater placed on a thermoelectric element. FIG. 5 is a diagram illustrating an example of a process of varying a channel using a thermoelectric element when a heater fails according to the present invention. FIG. 5 is a diagram illustrating another embodiment of the process of varying the channel using a thermoelectric element when the heater fails according to the present invention. Specific details for implementing the invention

[0012] The present invention is susceptible to various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing.

[0013] Terms such as first, second, A, B, etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0014] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0015] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" should be understood as not precluding the existence or addition of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification.

[0016] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains.

[0017] Terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0018] FIG. 3 shows a semiconductor laser (100) with a heater mounted on top of a thermoelectric element (10) in which the temperature of the upper plate is electrically controlled. Since the heater formed on the semiconductor laser diode chip can have various forms, it can be manufactured in various shapes, although not shown in this description. Typically, when a heater is mounted on a semiconductor laser diode chip, it is mounted on the upper part of the semiconductor chip, and thermal resistance occurs between the semiconductor laser diode chip (100) with the heater mounted thereon and the thermoelectric element (10) according to the structure of the semiconductor laser diode chip. Therefore, when power is applied to the heater of the semiconductor laser diode chip (100) with the heater mounted thereon placed on the thermoelectric element (10), the temperature of the light output active layer of the semiconductor laser diode chip (100) can be set differently from the temperature of the thermoelectric element (10) according to this heater power. Therefore, the temperature of the active layer of the semiconductor laser diode chip can be controlled regardless of the temperature of the thermoelectric element (10), and accordingly, the wavelength of the laser light emitted from the semiconductor laser diode chip can be controlled. As shown in FIG. 2, the temperature change of the active layer of the semiconductor laser diode chip due to the power of the heater mounted on the semiconductor laser diode chip is a phenomenon that occurs in a very short time. Therefore, the temperature of the thermoelectric element (100) is fixed at a predetermined constant temperature, and the power of the heater mounted on the semiconductor laser diode chip is changed to change the channel in a very short time, so a fast channel change time corresponding to class 2 of the NG-PON2 standard can be obtained. However, for various reasons, the operation of the heater may become unstable or the heater may not operate, and in this case, channel change cannot be performed, so a problem may arise in which the operation of the channel change system, which must change the channel by wavelength change, becomes difficult.At this time, if the temperature of the thermoelectric element (10) that the semiconductor laser diode chip (100) is in thermal contact with is controlled, the speed is slower than using a heater, but temporary channel variation and channel setting are possible, which helps in the operation of the system. To do this, regarding the heater mounted on the semiconductor laser diode chip (100) as shown in FIG. 4.

[0019] Step 1: Step to identify abnormal heater operation

[0020] Step 2: A step of stopping the operation of the heater or driving the power applied to the heater under specific conditions regardless of the channel.

[0021] Step 3: A step of changing the channel by varying the temperature of the thermoelectric element.

[0022] The channel can be varied and set by changing the temperature of the semiconductor laser diode chip (100) through a process including the above.

[0023] At this time, the first step: the step of detecting abnormal operation of the heater can use various methods, such as measuring the resistance of the heater and identifying the point of abnormal operation of the heater when the resistance changes above a preset resistance value, or measuring the resistance of the heater, measuring the rate of change of the resistance over time, and identifying the point of abnormal operation of the heater when the rate of change of the resistance over time changes above a preset value.

[0024] In the above process, the step of driving the power applied to the heater under specific conditions regardless of the channel in the second step means that even if the channel is fixed to one channel, the power applied to the heater does not necessarily have to be constant, and the power applied to the heater may change over time depending on whether a laser is generated from the laser diode chip. When the channel is varied by changing the power applied to the heater in the semiconductor laser diode chip (100) equipped with a heater, the average power consumption varies according to each channel, but even if the channel is fixed to one channel, the power applied to the heater may change over time, so the power applied to the heater does not need to be constant over time. Therefore, even when the channel is changed by the thermoelectric element, power that changes over time may be applied to the heater. However, in the case of a high temperature channel obtained by applying a high average power to the heater while the temperature of the thermoelectric element is constant, the same channel can be realized using a relatively low heater power and a relatively high thermoelectric element temperature, and in this case, since a relatively low average power is applied to the heater, the stability of the heater can be further increased.

[0025] If a malfunction occurs in the heater of the semiconductor laser diode chip (100) equipped with a heater, the system that exchanges information with this optical element must also be aware of this, so it can respond in the order shown in Fig. 5.

[0026] Step 1: A step of setting the heater power corresponding to each channel under a pre-selected thermoelectric element temperature condition, and a step of setting the thermoelectric element temperature corresponding to each channel under a pre-set heater power condition.

[0027] Step 2: Step to detect abnormal heater operation

[0028] Step 3: A step of reporting a heater abnormality to the system and notifying the change of the channel change mode from channel change using a heater to channel change using a thermoelectric element.

[0029] Step 4: A step of stopping the operation of the heater or driving the power applied to the heater under specific conditions regardless of the channel.

[0030] Step 5: A step of changing the channel by varying the temperature of the thermoelectric element.

[0031] Even if a malfunction occurs in the heater of the semiconductor laser diode chip (100) equipped with a heater, the system operation including channel variation is possible. In this description, the order of the examples of each step may be changed for convenience.

[0032] FIG. 6 shows a wavelength-selective filter in which the wavelength transmitted changes depending on the temperature, with a heater installed, and the wavelength-selective filter (200) with the heater installed is in thermal contact with a thermoelectric element (10). A thermal resistor not shown in the drawing may be additionally inserted between the heater of the wavelength-selective filter (200) with the heater installed and the thermoelectric element (10). Due to the thermal resistor not shown in the drawing, the temperature of the wavelength-selective filter (200) with the heater installed can be controlled differently from the temperature of the thermoelectric element (10), and depending on the size of this thermal resistor, the temperature of the wavelength-selective filter (200) with the heater installed can be varied at a very fast speed regardless of the temperature of the thermoelectric element (10). In this state, if a malfunction occurs in the heater installed in the wavelength-selective filter (200), the communication channel cannot be varied. In such cases, as previously explained, the temperature of the wavelength selective filter (200) equipped with the heater can be changed by stopping the operation of the heater or by adjusting the temperature of the thermoelectric element (10) while applying a constant power to the heater. Even in such cases, the wavelength selection channel of the wavelength-tunable light receiving element can be varied through the process of FIGS. 4 and FIGS. 5. In the case of the thermoelectric element (10) and the semiconductor laser diode chip (100) equipped with the heater that is in thermal contact with the thermoelectric element (10) or the wavelength selective filter (200) equipped with the heater that is in thermal contact with the thermoelectric element (10), if a malfunction occurs in the element that performs rapid channel adjustment by maintaining the thermoelectric element (10) at a predetermined constant temperature and adjusting the power of the installed heater, the system can be operated stably by stopping the power applied to the heater or changing the temperature of the thermoelectric element (10) while fixing the power at a constant level, thereby continuing the channel variation operation.

[0033] Furthermore, in NG-PON2, Class 2 is applied for corporate subscribers who primarily exchange large amounts of data, while Class 3 wavelength-tunable optical devices are applied for general residential subscribers. Therefore, it is possible to switch from Class 2 to Class 3 when the heater fails, or to switch between Class 2 and Class 3 regardless of heater failure. Consequently, in such cases, the assumption of heater failure is not required; instead, the system operation is made convenient by allowing users to arbitrarily configure the operation according to their convenience, either by adjusting the power consumed by the heater using a semiconductor laser diode chip equipped with a heater or a wavelength-selective filter equipped with a heater, or by varying the channel using a thermoelectric device. The mutual switching between Class 2 and Class 3 is implemented by exchanging predetermined signals with the system.

[0034] Although the channel variation time in this invention has been described as being limited to class 3 and class 2 of the NG-PON2 standard, it is clear that this invention can be applied to any system with a different channel variation time.

[0035] Although FIGS. 4 and 5 describe each process as being executed sequentially, this is merely an illustrative explanation of the technical concept of one embodiment of the present invention. In other words, a person skilled in the art to which one embodiment of the present invention belongs can modify and adapt the process in various ways, such as changing the order described in FIGS. 4 and 5 or executing one or more of the processes in parallel, without departing from the essential characteristics of one embodiment of the present invention; therefore, FIGS. 4 and 5 are not limited to a chronological order.

[0036] Meanwhile, the processes illustrated in FIGS. 4 and 5 can be implemented as computer-readable code on a computer-readable recording medium. A computer-readable recording medium includes all types of recording devices in which data that can be read by a computer system is stored. That is, a computer-readable recording medium includes storage media such as magnetic storage media (e.g., ROM, floppy disk, hard disk, etc.) and optical reading media (e.g., CD-ROM, DVD, etc.). In addition, the computer-readable recording medium can be distributed across networked computer systems, allowing computer-readable code to be stored and executed in a distributed manner. Explanation of the symbols

[0037] 10: Thermoelectric element 100: Heater-equipped semiconductor laser diode chip 110: Laser light emitted from a semiconductor laser diode 200: Wavelength-selective filter with variable transmitted wavelength equipped with a heater 210: Laser light incident on a wavelength-selective filter 220: Laser light reflected from a wavelength-selective filter

Claims

Claim 1 A method for controlling an optical element that is in thermal contact with a thermoelectric element, wherein the temperature of an active layer can be controlled by a heater, comprising: a process of measuring the resistance of the heater to determine whether the resistance changes above a preset resistance value or whether the rate of change of the heater resistance value over time changes above a preset value, thereby determining whether an abnormality has occurred in the heater; a process of stopping the operation of the heater or applying power that changes over time to the heater regardless of the channel; and a process of changing the temperature of the thermoelectric element to change the temperature of the optical element and changing the channel.

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