KR20220028256A - Laser device having double ring structure - Google Patents

Abstract

According to embodiments of the present invention, a laser device comprises: a first amplifier for generating first ASE light by receiving first light including at least one of a wavelength included in a C-band and a wavelength included in an L-band; a second amplifier for generating second ASE light by receiving second light including at least one of the wavelength included in the C-band and the wavelength included in the L-band; an optical splitter for outputting a part of light traveling a ring structure to the outside of the ring structure; a tunable filter for filtering light having the wavelength included in the C-band or L-band from the remaining light which is not output; an optical switch located in an optical path between the first and second amplifiers, and propagating the first ASE light to a first path facing a first splitter from the first amplifier and a second path facing the second amplifier from the first amplifier; and an optical coupler for combining lights of the first and second paths into single light to output the same to the optical splitter. Therefore, a decrease in light amplification efficiency in a specific wavelength range is eliminated.

Description

Laser device having a double ring structure {LASER DEVICE HAVING DOUBLE RING STRUCTURE}

Embodiments relate to a laser device, and more particularly, to a laser device having a doubling structure and in which optical amplification efficiency of an output optical signal does not decrease through switching.

Lights of different wavelengths propagate without interfering with each other. When information is carried on different wavelengths and transmitted over a single optical fiber, each piece of information propagates along the optical fiber without mutual interference. This transmission method is called a wavelength division multiplexing transmission method (WDM, Wavelength Divisional Multiplexing). Wavelength division multiplexing technology can greatly increase the information transmission capacity of optical fibers, and is widely used in the optical communication field.

In the field of optical communication, information is transmitted on an optical signal emitted from a laser device. Lasers have various optical properties such as light intensity, wavelength range, line-width, and lasing interval (FSR). Therefore, it is necessary to select a laser having suitable optical properties according to the intended application.

An optical characteristic suitable for the wavelength division multiplexing technique is a wavelength range of 1530 nm-1625 nm, that is, a wavelength range of C-band (conventional band) and L-band (long wave length band). High-performance transmission without loss of information is possible only when the output power of the optical signal amplified inside the laser is high in the corresponding wavelength range.

Therefore, the output power of the optical signal amplified inside the laser in the C-band and/or L-band range has an overall low intensity, or a sub-range (eg, C-band and/or L-band) included in the corresponding region. In the case of having a low intensity in a specific wavelength range), there is a limit to having low transmission performance.

Registered Patent Publication No. 10-0957133 (2010.05.11.)

According to an aspect of the present invention, it is possible to provide a laser device in which a decrease in optical amplification efficiency in a specific wavelength range that may occur within a C-band and/or an L-band range is eliminated.

A laser device according to an embodiment of the present invention has a ring structure for circulating a C-band or L-band wavelength component. The laser device includes: a first amplifier for receiving first light including at least one of a wavelength belonging to C-band and a wavelength belonging to L-band to generate a first ASE light; a second amplifier for receiving a second light including at least one of a wavelength belonging to the C-band and a wavelength belonging to the L-band to generate a second ASE light; a light splitter configured to output a portion of the light traveling through the ring structure to the outside of the ring structure; a tunable filter for filtering light having a wavelength belonging to C-band or L-band from the remaining light that is not output; located in the optical path between the first amplifier and the second amplifier, the first ASE optical in a first path from the first amplifier to a first splitter or in a second path from the first amplifier to the second amplifier an optical switch to propagate; and a light coupler for combining the light of the first path and the second path into a single light and outputting the light to the light splitter.

In one embodiment, the optical switch may be configured to: couple the second path for a first time to cause a first ASE light generated by the first amplifier to travel to the second amplifier.

In one embodiment, the optical switch may be configured to: couple the first path for a second time to cause a first ASE light generated by the first amplifier to travel to the optical coupler.

In one embodiment, the optical switch may be further configured to have a constant switching time for changing the optical path in order to prevent the waveform of the light output to the outside of the ring structure from being unintentionally transformed into the output waveform.

In an embodiment, the tunable filter may be configured to set a filtering wavelength based on an electrical signal. In the tunable filter, the wavelength belonging to the L-band is set as the filtering wavelength for the first time to pass the component having the corresponding wavelength, and the wavelength belonging to the C-band for the second time is set as the filtering wavelength to obtain the corresponding wavelength the components with it are passed through.

In an embodiment, a first electrical signal corresponding to a wavelength range belonging to the L-band for the first time is applied to the tunable filter, and a second electrical signal corresponding to a wavelength range belonging to the C-band for the second time period A signal may be applied to the variable filter.

In one embodiment, an initial electrical signal is applied to the variable filter before the electrical signal of the first range or the second range is applied, and after the electrical signal of the first range and the electrical signal of the second range is applied An initial electrical signal may be applied. The initial electrical signal is set based on a voltage and a pressure gradient of the piezoelectric material in the variable filter, and a voltage section corresponding to the L-band range and the voltage section corresponding to the C-band range.

In an embodiment, the initial voltage of the initial imputation signal may be a voltage higher than a voltage section corresponding to the L-band range or a voltage section corresponding to the C-band range.

The laser device according to an embodiment of the present invention has a double ring structure and is configured to eliminate a phenomenon of reduction in optical amplification efficiency that may occur in a specific wavelength range among L-band and/or C-band wavelength ranges.

As a result, it has high performance in a wavelength division multiplexing (WDM) communication system.

Effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

In order to more clearly explain the technical solutions of the embodiments of the present invention or the prior art, drawings necessary for the description of the embodiments are briefly introduced below. It should be understood that the drawings below are for the purpose of explaining the embodiments of the present specification and not for the purpose of limitation. In addition, some elements to which various modifications such as exaggeration and omission have been applied may be shown in the drawings below for clarity of description.
1 is a conceptual configuration diagram of a laser device according to an embodiment of the present invention.
2 is a diagram for explaining the ASE optical output generated in the amplifier 104, according to an embodiment of the present invention.
3A and 3B are diagrams for explaining an ASE light output generated by the amplifier 108 according to various embodiments of the present disclosure.
4 is a diagram illustrating a relationship between a piezoelectric voltage and a filtering wavelength according to an embodiment of the present invention.
5 is a diagram for explaining a relationship between a filtering wavelength and a switching operation according to an embodiment of the present invention.
6A and 6B are diagrams for explaining the characteristics of the optical signal output from the amplifier 108 according to an experimental example of the present invention.

Embodiments will be described herein with reference to the accompanying drawings, however, the principles disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the detailed description of the invention, detailed descriptions of well-known features and techniques may be omitted to avoid unnecessarily obscuring the features of the embodiments.

The terminology used in the present invention is only used to describe the confirmed embodiment, and is not intended to limit the present invention. As used in the present invention and the appended claims, the singular expression is intended to include the plural expression unless the context clearly dictates otherwise. It should also be understood that the term “and/or” as used herein includes any or all possible combinations of one or more related listed items.

The terms first, second and third etc. are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of "comprising" specifies a particular characteristic, region, integer, step, operation, element and/or component, and the presence or absence of another characteristic, region, integer, step, operation, element and/or component It does not exclude additions.

In the present specification, the wavelength band is an optical communication band (Telecommunication bands), as shown in Table 1 below, according to the standards of the International Telecommunication Union Telecommunication Standard Sector (ITU-T).

fiber optic band Wavelength range (nm) O-Band (Original) 1260-1360 nm E-Band (Extended) 1360-1460 nm S-Band (Short Wavelength) 1460-1530 nm C-Band (Conventional) 1525-1565 nm L-band (Long wavelength) 1565-1625 nm U-band (Ultralong wavelength) 1625-1675 nm

Accordingly, in the present specification, light (or component) belonging to the C-band refers to light having a wavelength of any one of 1525 to 1565 nm, and light (or component) belonging to the L-band is any one of 1565-1625 nm. refers to light with a wavelength of In this specification, amplified light is not interpreted as amplification in ASE (Amplified Spontaneous Emission) light generated by amplifying light energy in an amplifier. Specifically, amplification in ASE light means energy amplification through a 980 nm pump laser diode, but amplifying light in the present invention means SE (Stimulated Emission).

Hereinafter, specific details for carrying out the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual configuration diagram of a laser device according to an embodiment of the present invention.

Referring to FIG. 1 , a laser device 1 includes a pump laser diode 101 , 102 , amplifiers 104 , 108 , an optical switch 106 , an optical coupler 110 , an optical splitter 111 , a variable filter ( 112). The laser device 1 has a ring structure that amplifies and circulates a laser light signal traveling in an optical path. Some of the optical signals amplified in the ring structure are output to the outside.

The optical path is a path through which a laser optical signal travels, and includes, for example, an optical fiber, an optical waveguide, and the like.

The laser device 1 has a ring structure for amplifying a C-band component (hereinafter, “C-band ring structure”) and a ring structure for amplifying an L-band component (hereinafter “L-band ring structure”). A double ring structure including

As shown in FIG. 1 , the C-band ring structure includes a laser diode 101 for a pump, an amplifier 104 , an optical splitter 111 , and a tunable filter 112 . Meanwhile, the L-band ring structure includes a laser diode 102 for a pump and an amplifier 108 .

The laser diode 101 for pump injects optical energy into a C-band ring structure, or a C-band ring structure and an L-band ring structure. The laser diode 102 for the pump injects light energy into the L-band ring structure. Such light energy may be used as pumping energy for amplifying light energy.

For example, the laser diodes 101 and 102 for pumps inject pumping energy having a wavelength of 970 to 990 nm (eg, 980 nm) into a C-band ring structure or an L-band ring structure.

The light energy injected by the laser diode 101 or 102 for the pump is transmitted to the amplifier 104 or 108, which causes the amplifier 104 or 108 to output the amplified light.

In addition, the optical path is configured to have a point where the C-band ring structure and the L-band ring structure diverge and combine.

The laser device 1 of FIG. 1 has an optical switch 106 disposed at a point where the C-band ring structure and the L-band ring structure diverge, and a C-band ring structure and L-band ring structure. and a light coupler 110 disposed at the point of being coupled.

The optical switch 106 allows the optical signal of the input terminal to proceed to the optical paths of the different output terminals. In one embodiment, the optical switch 106 has an output that directs the optical path of the input to the amplifier 108 . In addition, the optical switch 106 has an output terminal that is not input to the amplifier 108 and allows the optical path to proceed to the optical splitter 111 through the optical coupler 110 . That is, the optical switch 106 optically connects the optical path of the C-band ring structure and the L-band ring structure, or one optical path in the C-band ring structure and the C-band optical path. configured to connect different optical paths within the ring structure.

In this way, the optical switch 106 is configured to perform a switching operation for allowing the input optical signal to proceed in the L-band ring structure or in the C-band ring structure. In a specific embodiment, the laser device 1 may further include a switching control module (not shown) for controlling the switching operation of the optical switch 106 . The switching operation of the optical switch 106 will be described in more detail with reference to FIG. 5 below.

Meanwhile, the amplifier 104 or the amplifier 108 is configured to amplify at least a portion of light (or components) having a wavelength of C-band and/or L-band in the input optical signal.

In an embodiment, the amplifier 104 may amplify a component having a wavelength included in the C-band to be greater than a component having a wavelength included in the L-band. That is, the amplifier 104 is configured to mainly amplify light of a wavelength belonging to the C-band.

The range and/or strength of the components to be amplified in the amplifier 104 depend on the characteristics of the amplifier 104 , such as the amplification medium or length. If these characteristics are changed, the amplification performance of the amplifier 104 may be adjusted. Then, different light output results may be obtained through changes in the characteristics of the amplifier 104 .

The amplifier 104 may be, for example, an Er-doped fiber amplifier (EDFA), but is not limited thereto. When the amplifier 104 is an EDFA, the light output generated by the amplifier 104 is referred to as Amplified Spontaneous Emission (ASE) light.

2 is a diagram for explaining the ASE optical output generated in the amplifier 104, according to an embodiment of the present invention.

Referring to FIG. 2 , the amplifier 104 receives a component belonging to the C-band in optical energy, that is, a wavelength within the range of 1525-1565 nm, from the laser diode 101 for the pump, and outputs ASE light. As shown in FIG. 2, components belonging to the C-band are mainly amplified. Some components that are amplified from components not belonging to the C-band belong to a section adjacent to the C-band in the L-band range. As shown in FIG. 2, some of the components are amplified with a lower intensity than components belonging to the C-band. As such, the amplifier 104 hardly amplifies light that does not belong to the C-band. On the other hand, light outside the ASE region is almost ignored.

The optical energy generated by the amplifier 104 may be propagated by the optical switch 106 to the optical coupler 110 .

Additionally, optical energy generated by the amplifier 104 may be passed to the amplifier 108 by an optical switch 106 , where it may assist in amplifying the amplifier 108 . When some or all of the ASE light output from the amplifier 104 proceeds to the amplifier 108 of the L-band ring structure, the amplification region and/or the degree of amplification in the L-band ring structure is increased.

In one embodiment, amplifier 108 is configured to amplify components belonging to the L-band in light traveling in the optical path. The amplifier 108 may amplify a component having a wavelength included in the L-band more than a component having a wavelength included in the C-band. Then, the wavelength belonging to the L-band is mainly amplified by the amplifier 108 .

In addition, the light amplified and output by the amplifier 108 may further include some of the components that do not belong to the L-band in the input optical signal. Some components that are amplified from the components that do not belong to the L-band belong to a section adjacent to the L-band in the C-band range. The partial component is amplified with a lower intensity than the component belonging to the L-band.

Amplifier 108 may also change characteristics of the amplifier, such as amplification medium or length, in order to change the range and intensity to be amplified, similar to amplifier 104 .

The amplifier 108 may be, for example, an Er-doped fiber amplifier (EDFA), but is not limited thereto. When amplifier 108 is an EDFA, amplifier 108 generates an ASE optical output.

The amplifier 108 outputs the component belonging to the L-band in the optical energy input by the laser diode 101 or 102 for the pump, that is, the ASE light having a wavelength in the range of 1565-1625 nm.

The ASE light output from the amplifier 104 and the light energy injected from the pump laser diode 102 proceed to the L-band ring structure through the amplifier 108 . Here, the optical energy (eg, ASE light) generated by the amplifier 104 is passed to the amplifier 108 by the optical switch 106 . The energy input to the amplifier 108 includes light energy injected from the amplifier 104 and/or light energy injected from the pump laser diode 102 .

The optical energy of the amplifier 104 may help the amplifier 108 generate ASE light with predominantly increased intensity of components belonging to the L-band. The laser device 1 including the optical switch 106 obtains the ASE light of the EDFA in the form of a graph shown in FIG. 3 below.

3A and 3B are diagrams for explaining an ASE light output generated by the amplifier 108 according to various embodiments of the present disclosure.

When some or all of the light of the pump laser diode 102 and the ASE light generated by the amplifier 104 of FIG. 2 is input to the amplifier 108 , the ASE light of FIG. 3 may be generated by the amplifier 108 .

The optical power output from the amplifier 108 depends on the power of the input light and/or the double ring structure.

As shown in Fig. 3B, when only the input light of the laser diode 102 for pump is input to the amplifier 108, the ASE light having a higher power of the input light of 370 mW compared to the input light of 205 mW is output.

On the other hand, due to the double ring structure of the laser light device 1 of FIG. 1 , the light passing through the amplifier 104 and the amplifier 108 has a higher power compared to the case of having only a single amplifier (eg, 108 ). As discussed above, the optical energy of the amplifier 104 may help the amplifier 108 to generate ASE light with predominantly increased intensity of components belonging to the L-band. When the ASE light of the amplifier 104 of 80 mW and the light of the laser diode 102 for the pump of 205 mW are input to the amplifier 108, as shown in FIG. ASE light with high optical power is output.

At least a portion of the ASE light generated by the amplifiers 104 and/or 108 is input to a tunable filter 112 .

The tunable filter 112 is configured to filter a component corresponding to a preset filtering wavelength from the ASE light output input to the filter 112 .

In one embodiment, the tunable filter 112 may be a piezoelectric element-based tunable filter. The piezoelectric element-based variable filter includes a piezoelectric material. The tunable filter 112 is configured to adjust a filtering wavelength according to an applied electrical signal. For example, in the variable filter 112, the filtering wavelength is adjusted according to the voltage of the applied electric signal. The variable filter 112 includes a piezoelectric material. The piezoelectric material may include, for example, at least one material selected from the group including aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lead titanate (PbTiO3), and combinations thereof. However, the present invention is not limited thereto, and may include various piezoelectric materials whose electrical signals change according to pressure.

In other embodiments, the tunable filter 112 may be various optical filters capable of filtering a wavelength of a desired band, ie, an L band or a C band.

In a specific embodiment, the laser device 1 may further include a filter control module (not shown) for controlling the tunable filter 112 . The filter control module is configured to apply a filtering control signal to the variable filter 112 to apply a piezoelectric voltage to the variable filter 112 .

The tunable filter 112 is configured to pass the light corresponding to the filtering wavelength in the light of the input stage. The passed light has a signal according to the filtering wavelength control voltage, and the light energy is converted into an optical signal by the variable filter 112 .

4 is a diagram illustrating a relationship between a piezoelectric voltage and a filtering wavelength according to an embodiment of the present invention.

Referring to FIG. 4 , in the variable filter 112 , a filtering wavelength (or filtering frequency) according to an applied voltage (ie, a piezoelectric voltage) may be linearly adjusted. The control module may apply a voltage corresponding to the filtering wavelength (or filtering wavelength) of FIG. 4 to set a desired filtering wavelength to the tunable filter 112 .

Then, the optical signal traveling through the optical path of the laser device 1 is the pumped optical energy input from the pump laser diodes 101 and 102, the filtered optical signal having a wavelength belonging to the C-band, and/or the L- It contains a filtered optical signal having a wavelength belonging to the band. The light of the optical path having the above-described various components is input to the wavelength division multiplexers 103 and 107, multiplexed, and output.

In the laser device 1 having such a double ring structure, a portion of the light in the optical path is emitted to the outside of the ring by the optical splitter 111 . For example, as shown in FIG. 1 , a portion of the light passing through the optical coupler 110 may be branched from the C-band ring structure by the optical splitter 111 .

Further, in certain embodiments, the laser device 1 includes an optical isolator disposed at the output of the amplifier 104 and/or 108, respectively, so that the ASE light generated by the amplifier 104 or 108 does not travel in the reverse direction. It may further include (105 and/or 109). In addition, the laser device 1 may further include an optical isolator 113 disposed at the output end of the tunable filter 112 .

The switching operation of the optical switch 106 is correlated with the filtering operation of the variable filter 112 . That is, the switching operation of the optical switch 106 is performed based on the filtering wavelength of the variable filter 112 so that the optical path of the output terminal is connected.

5 is a diagram for explaining a relationship between a filtering wavelength and a switching operation according to an embodiment of the present invention.

Referring to FIG. 5 , in the tunable filter 112 , the filtering wavelength may be adjusted during the switching period. The switching period includes an L-band sampling time for filtering a wavelength belonging to the L-band and a C-band sampling time for filtering a wavelength belonging to the C-band. The L-band sampling time may be referred to as an L-band sampling period, and the C-band sampling time may be referred to as a C-band sampling period.

In an embodiment, the laser device 1 may perform an L-band sweeping operation during an L-band sampling time. Also, the laser device 1 may perform a C-band sweeping operation during the C-band sampling time.

During the L-band sampling time, the optical filter 112 filters the wavelength signal in the L-band and circulates it to the optical circuit, the switching control module causes the optical switch 106 to make an optical path to the optical amplifier 108 . Switching causes the optical signal output from the amplifier 104 to proceed to the amplifier 108 .

The variable filter 112 has a wavelength belonging to the L-band as a filtering wavelength during the L-band sampling time. For example, the tunable filter 112 is controlled to have a wavelength in the range of 1565-1625 nm as a filtering wavelength during the L-band sampling time. Then, in the input light of the tunable filter 112, a wavelength component belonging to the L-band and set as the filtering wavelength is filtered.

The filter control module applies an electric signal corresponding to the wavelength of the L-band to the variable filter 112 for the L-band sampling time. For example, a linear voltage may be applied as shown in FIG. 5 during the L-band sampling time.

Meanwhile, in the laser device 1 during the L-band sampling time, light of the L-band wavelength is mainly amplified. This is because the variable filter 112 passes a component of some or all of the ASE light generated by the amplifier 108 and does not pass most or all of the ASE light generated by the amplifier 104 . The filtered optical signal circulates through the optical circuit at a high speed and generates signal amplification through ST (Stiumulated Emission). The filtered optical signal is again greatly amplified by the optical amplifier 108, some of the amplified optical signal is output from the optical splitter 111, and the rest is circulated for amplification again.

The ASE light output from the amplifier 108 during the L-band sampling time is an optical isolator 109, an optical coupler 110, an optical splitter 111, a tunable filter 112, an optical isolator 113, and wavelength splitting. The multiplexer 103, the amplifier 104, and the optical switch 106 are cycled back to the amplifier 108 in sequence, during which energy loss occurs in all optical components. In certain embodiments, since high light absorption occurs in the amplifier 104 , the amplifier 108 is configured such that the power of the ASE light is large. To this end, the amplifier 108 is configured to have amplification characteristics such as an amplification medium or length corresponding thereto.

When the operation time of the laser device 1 elapses after the L-band sampling time and reaches the C-band sampling time, the optical switch 106 transmits the ASE light output from the amplifier 104 to the optical switch 106 . Proceed directly to the optical coupler 110 . Here, the meaning of “going straight through” means not going through the amplifier 108 to the optical coupler 110 , and going without passing through any component between the optical switch 106 and the optical coupler 110 . does not mean to do

The control module allows the optical switch 106 to connect the optical path of the C-band ring structure while the optical switch 106 filters the C-band optical signal. For example, when the start time of the C-band sampling time is reached, the switching control module may cause the ASE light of the amplifier 104 to go directly to the optical coupler 110 without going from the optical switch 106 to the amplifier 108 . The optical switch 106 is controlled to switch. Then, during the C-band sampling time, the optical filter 112 filters the wavelength signal in the C-band and circulates it to the optical circuit.

The tunable filter 112 has a wavelength belonging to the C-band as a filtering wavelength during the C-band sampling time. For example, the tunable filter 112 is controlled to have a wavelength in the range of 1525-1565 nm as a filtering wavelength for the C-band sampling time in the input light, and then, while belonging to the C-band in the input light of the tunable filter 112 , The wavelength component set as the filtering wavelength passes through the filter and continues.

The filter control module applies an electrical signal corresponding to the wavelength of the C-band to the variable filter 112 during the C-band sampling time. The filtering wavelength may be adjusted within the C-band range during the C-band sampling time. For example, as shown in FIG. 5 , a linear voltage may be applied during the C-band sampling time.

Meanwhile, in the laser device 1 during the C-band sampling time, light having a wavelength of C-band is mainly amplified. This is because the variable filter 112 passes most or all of the components belonging to the C-band in the ASE light generated by the amplifier 104 and does not pass most or all of the components belonging to the L-band. The filtered optical signal circulates through the optical circuit at a high speed and generates signal amplification through ST (Stiumulated Emission). The filtered optical signal is again greatly amplified by the optical amplifier 104, and the optical signal including the amplified C-band component is partially output from the optical splitter 111, and the rest is circulated for amplification again.

In this way, only light of a specific wavelength for each time period is amplified and circulated in the laser device 1 .

In one embodiment, the optical switch 106 is further configured to have a transition time between the L-band sampling time and the C-band sampling time. The switching time is to prevent a waveform of light output to the outside of the ring structure from being unintentionally transformed into an output waveform.

For example, the optical switch 106 connects the optical path to the amplifier 108 during the L-band sampling time, and when the switching time is reached, performs a switching operation and then connects another optical path for the C-band sampling time do.

Without the switching time, the laser device 1 may have an unintended operation that is not an operation intended by the designer (eg, a designed amplifying, cycling and/or filtering operation). The unintentional operation includes, for example, a region in which an output power is decreased or a graph form of the output power according to an output frequency is generated as an unintended output waveform.

The laser device 1 can accurately perform the designed amplification, circulation and/or filtering operations and the like by having a switch time.

In addition, the variable filter 112 is further configured to apply an initial electrical signal before the electrical signal corresponding to the filtering wavelength belonging to the L-band or the electrical signal corresponding to the filtering wavelength belonging to the C-band is applied. The filter control module transmits a control signal so that an initial voltage is applied to the variable filter 112 before performing the filtering operation of the C-band or L-band component within one period.

While the corresponding initial electric signal is applied, the filter control module may apply the initial electric signal so that the light amplification medium constituting the amplifier 104 or 108 has a lifetime of spontaneous emission. The optical amplification medium used in the optical amplifier 104 or 108, for example a light doped rare earth material, has an energy state. This is because, during the first operation, a lifetime problem, which is the time required for spontaneous emission from a specific energy state to another energy state, may occur.

The filter control module causes the variable filter 112 to perform the filtering operation of the L-band or C-band component, and then causes the initial voltage of the initial electrical signal to be applied again. For example, when the control voltage moves away from the initial voltage as shown in FIG. 5 , a control signal returning to the initial voltage value from the last control voltage applied for filtering may be applied to the variable filter 112 . In some embodiments, the process of returning from the value of the last control voltage to the value of the initial voltage is performed non-immediately, that is, gradually by applying a control signal including a section having a constant slope, and the return time is the control stabilization time (or ramp stabilizing time).

Also, the laser device 1 may be further configured to repeat the switching operation for the L-band sampling time and the switching operation for the C-band sampling time per a plurality of periods. Then, the filtering operation corresponding to each switching operation is linked to perform both the amplification of the C-band optical signal and the L-band optical signal per one cycle.

In the filtering and amplification process, there is no difference in transmission characteristics for each wavelength or reflection characteristics for each wavelength on an optical path that lowers the amplification efficiency of a specific wavelength region. In the laser device 1, the change of the optical path associated with the filtering and amplification process is implemented by a switching operation, and a light coupler having a difference in transmission characteristics for each wavelength and/or reflection characteristics for each wavelength is not used. Because.

The switching period and switching time are the switching specifications of the optical switch 106 , the length of the ring structure of the L-band, the length of the ring structure of the C-band, the voltage of the piezoelectric material in the variable filter 112 and the filtering wavelength It is determined depending on a relationship (eg, a rate of change of wavelength per voltage) and the like.

As such, the switching period is a time taken to adjust the entire wavelength of the L-band range (ie, L-band sampling time) and a time taken to control the entire wavelength of the C-band range (ie, C-band sampling time) or may further include a transition time.

The switching period may be, for example, 9,000 us or more and 11,000 us or less, or approximately 10,000 us. The switching time in the switching period may be, for example, 100 us or more, approximately 200 us or more.

The initial electrical signal (eg, initial voltage) applied to the variable filter 112 is set to an arbitrary value above the minimum threshold voltage that can control both the L-band range and the C-band range based on the piezoelectric voltage and pressure gradient of the piezoelectric material. can be decided. In certain embodiments, the initial voltage value may be determined as a value near a threshold voltage in order to prevent too much return energy after adjusting the filtering wavelength from being consumed.

For example, as shown in FIGS. 4 and 5 , the initial voltage may be approximately 30V, but is not limited thereto, and the initial voltage is greater than or equal to the voltage range of the C-band to the L-band (for example, 8 or 11V).

The optical coupler 110 may be, for example, a splitter or a coupler. Also, the optical coupler 110 may be configured to synthesize an optical signal having an L-band ring structure and an optical signal having a C-band ring structure, for example, 50:50. Optical signals of different optical paths are combined into a single optical signal by the optical coupler 110 .

The optical splitter 111 may be, for example, a splitter or a coupler.

In the above-described embodiments, the optical switch 106 and the tunable filter 112 of the laser device 1 are individually controlled by a plurality of separately implemented control components (a filter control module and a switching control module). described, but not limited thereto. The switch control module and the filter control module may be implemented as a single control module, wherein the single control module may be implemented to transmit respective control signals to the optical switch 106 and the variable filter 112 of the laser device 1 . may be

6A and 6B are diagrams for explaining the characteristics of the optical signal output from the amplifier 108 according to an experimental example of the present invention.

In the above experimental example, the laser device 1 used 980 nm pump laser diodes 101 and 102 to form a C-band ring-structured erbium-doped fiber (EDF) with a length of 15 m and an L-band ring-structure erbium with a length of 18 m, respectively. It has a doped fiber (EDF), and the optical signal that has been filtered out of the spontaneous emission (ASE) of the previous cycle is amplified in an erbium-doped fiber (EDF).

Referring to FIG. 6A , the output power of the optical signal output from the amplifier 108 has positive dBm at all wavelengths in the C-band and L-band ranges.

Referring to FIG. 6a , in the double-ring structure using two EDFAs, larger L-band amplification can be obtained compared to the case of using a single EDFA. A portion of Amplified Spontaneous Emission (ASE) light in the C-band component that is not mainly amplified during the L-band sampling time using the Optical Switch 106 is used to amplify the L-band component to amplify the larger L-band can be obtained It is also possible to obtain a larger C-band amplification compared to the case of using a single EDFA.

In particular, in the laser device 1, an optical signal around 1570 nm, for example, 1565 to 1573 nm, does not have a relatively low output power compared to other parts.

On the other hand, if the laser device 1 includes an optical coupler having transmission characteristics of 191.8-200.0 THz and 1500-1564 nm instead of the optical switch 106, the overall power of the light amplified in the circuit is 0 dBm or less. There is a disadvantage in that light in the vicinity of 1570 nm, for example, 1565 to 1573 nm, has a relatively low output power compared to the power of other wavelengths.

Also, referring to FIG. 6B , the optical signal output from the amplifier 108 has a half maximum width of about 6.178 GHz.

As such, when the laser device 1 including the optical switch 106 is used, the optical amplification efficiency is not reduced in a specific wavelength range among the L-band and/or C-band wavelength ranges.

Although the present invention described above has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and variations of the embodiments are possible therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Accordingly, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

1: laser device
101, 102: laser diode
103, 107: wavelength division multiplexer
104, 108: amplifier
105, 109, 113: optical isolators
106: optical switch
110: optical coupler
111: optical splitter
112: variable filter

Claims (8)

A laser device having a ring structure for circulating a C-band or L-band wavelength component, the laser device comprising:
a first amplifier for receiving first light including at least one of a wavelength belonging to the C-band and a wavelength belonging to the L-band to generate a first ASE light;
a second amplifier for receiving a second light including at least one of a wavelength belonging to the C-band and a wavelength belonging to the L-band to generate a second ASE light;
a light splitter configured to output a portion of the light traveling through the ring structure to the outside of the ring structure;
a tunable filter for filtering light having a wavelength belonging to C-band or L-band from the remaining light that is not output;
located in the optical path between the first amplifier and the second amplifier, the first ASE optical in a first path from the first amplifier to a first splitter or in a second path from the first amplifier to the second amplifier an optical switch to propagate; and
and a light coupler for combining the light of the first path and the second path into a single light and outputting the light to the light splitter.
The method of claim 1 , wherein the optical switch comprises:
The laser device of claim 1, wherein the first ASE light generated by the first amplifier is propagated to the second amplifier by connecting the second path for a first time.
3. The method of claim 2, wherein the optical switch comprises:
and connecting the first path for a second time to cause the first ASE light generated by the first amplifier to travel to the optical coupler.
4. The method of claim 3, wherein the optical switch comprises:
The laser device, characterized in that it is further configured to have a constant switching time to change the optical path in order to prevent the waveform of the light output to the outside of the ring structure from being transformed into an unintended output waveform.
4. The method of claim 3,
The tunable filter is configured to set a filtering wavelength based on an electrical signal,
During the first time, a wavelength belonging to the L-band is set as a filtering wavelength to pass a component having the corresponding wavelength,
A wavelength belonging to the C-band during the second time period is set as a filtering wavelength, and the component having the corresponding wavelength is passed through the laser device.
6. The method of claim 5,
During the first time, a first electrical signal corresponding to a wavelength range belonging to the L-band is applied to the tunable filter, and for the second time, a second electrical signal corresponding to a wavelength range belonging to the C-band is applied to the tunable filter Laser device, characterized in that applied to.
7. The method of claim 6,
An initial electrical signal is applied to the variable filter before the electrical signal of the first range or the second range is applied,
After the electrical signal of the first range and the electrical signal of the second range are applied, the initial electrical signal is applied again,
The initial electrical signal is set based on a voltage and a pressure gradient of the piezoelectric material in the variable filter, and a voltage section corresponding to the L-band range and a voltage section corresponding to the C-band range.
8. The method of claim 7,
The initial voltage of the initial imputation signal is a voltage higher than a voltage section corresponding to the L-band range or a voltage section corresponding to the C-band range.

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