KR20040078924A - Mode-locked fabry-perot laser device having multiple resonators and optical source for wavelength division multiplexing system using it - Google Patents

Abstract

PURPOSE: A mode-locked Fabry-Perot laser device provided with a multi-resonator and wavelength division multiplexing light source using the same are provided to make the oscillation modes dense by providing with a first and a second resonators. CONSTITUTION: A mode-locked Fabry-Perot laser device(200) provided with a multi-resonator includes a Fabry-Perot layer(210) provided with a first reflector(212) and a second reflector(214) and a reflective material(234) as a third reflector. The third reflector at the outside of the Fabry-Perot laser(210) and forms a second resonator together with the first resonator.

Description

Wavelength-locked Fabry-Perot laser device with multiple resonators and wavelength-division multiplexed light source using the same. {MODE-LOCKED FABRY-PEROT LASER DEVICE HAVING MULTIPLE RESONATORS AND OPTICAL SOURCE FOR WAVELENGTH DIVISION MULTIPLEXING SYSTEM USING IT}

FIELD OF THE INVENTION The present invention relates to light sources for optical communications, and more particularly to Fabry-Perot lasers.

A wavelength division multiplexed (WDM) passive optical network (PON) provides a very high speed broadband communication service using a unique wavelength assigned to each subscriber. Thus, the confidentiality of the communication is assured, and it is easy to accommodate the expansion of the separate communication service or communication capacity required by each subscriber, and the number of subscribers can be easily expanded by adding the unique wavelength to be given to the new subscriber. have. Despite these advantages, the central office (CO) and each subscriber need a light source of a specific oscillation wavelength and an additional wavelength stabilization circuit for stabilizing the wavelength of the light source. Due to this, the wavelength division multiplexing passive optical subscriber network has not been put to practical use yet. Therefore, in order to implement a passive optical network of wavelength division multiplexing, it is necessary to develop an economical wavelength division multiplexing light source.

The wavelength division multiplexed light source includes a distributed feedback laser array (DFB laser array), a multi-frequency laser (MFL), a spectrum-sliced light source, and a non-interfering light source. Mode-locked Fabry-Perot laser with incoherent light has been proposed. Distributed feedback laser arrays and multi-wavelength lasers are expensive components that require complex wavelengths and accurate wavelength selectivity and wavelength stabilization for wavelength division multiplexing. Spectral dividing light sources, which are being actively studied in recent years, can provide a large number of wavelength-divided channels by spectral dividing a wide bandwidth of light using an optical filter or a waveguide grating router (WGR). Can be. Therefore, the spectral splitting light source does not need a light source having a specific oscillation wavelength, and also does not need a device for wavelength stabilization. Such spectral split light sources include light emitting diodes (LEDs), superluminescent diodes (SLDs), Fabry-Perot lasers (FP lasers), and fiber amplifier light sources. , Ultra-short optical pulsed light source and the like have been proposed.

Light emitting diodes and ultra-light emitting diodes have a very wide and inexpensive optical bandwidth, but have a low modulation bandwidth and output power, making them suitable as light sources for upstream signals with lower modulation rates than downlink signals. Fabry-Perot lasers are inexpensive, high-power devices or have a narrow bandwidth that cannot provide a large number of wavelength-divided channels. The disadvantage is that the degradation is severe. Ultra-short pulsed light source has a very wide optical bandwidth and coherent, but the oscillation wavelength is low stability, and the pulse width is only a few ps, difficult to implement. The optical fiber amplifier light source may spectrally split the amplified spontaneous emission light (ASE light) generated in the optical fiber for amplification to provide a large number of wavelength-divided high power channels. However, such spectral split light sources must separately use expensive external modulators, such as LiNbO ₃ modulators, to transmit different data over multiple channels.

The Fabry-Perot lasers, which are immersed in incoherent light, are subjected to spectral splitting of a wide bandwidth of light generated by an incoherent light source, such as a light emitting diode or a fiber amplifier light source, using an optical filter or waveguide diffraction grating. By injecting light into a Fabry-Perot laser without an isolator, it outputs wavelength locked light. That is, the Fabry-Perot laser outputs light in an oscillation mode that matches the wavelength of the spectral divided light injected therein. Fabry-Perot lasers immersed in non-coherent light have the advantage of being able to transmit data more economically by directly modulating the data signal. However, in order for a Fabry-Perot laser to output wavelength locked light suitable for high speed long distance transmission, a wide bandwidth high power incoherent light must be injected. In addition, when temperature control is not performed, the oscillation mode is changed when there is a change in the external temperature, which causes the light output to become unstable because the oscillation mode of the Fabry-Perot laser deviates from the wavelength of the spectral divided light injected. .

1 is a view showing the configuration of a conventional Fabry-Perot laser, Figures 2 to 5 are views for explaining the operating characteristics of the Fabry-Perot laser shown in FIG. The Fabry-Perot laser 110 has a first reflector 112 at one end thereof, a second reflector 114 at the other end thereof, and the first and second reflectors 112 and 114 form a resonator. do. The first reflector 112 has a relatively high reflectance, and the second reflector 114 opposite to the first reflector 112 has a relatively low reflectance.

2 shows the oscillation mode spectrum of the Fabry-Perot laser 110 at a point before the wavelength immersion. The Fabry-Perot laser 110 has a plurality of oscillation modes 116 located at wavelength intervals depending on the length of the resonator and the gain characteristics of the material. 3 shows an intensity profile of light 120 injected from the outside through the second reflector 114 of the Fabry-Perot laser 110. 4 shows an output spectrum of the Fabry-Perot laser 110 wavelength-locked by the injection light 120. The oscillation modes 116 that do not match the wavelength of the injection light 120 are suppressed, and the light 130 of the oscillation mode 116 that matches the wavelength of the injection light 120 is amplified and output. This phenomenon is called "wavelength locking" phenomenon. 5 illustrates a case in which the oscillation mode spectrum of the Fabry-Perot laser 110 is shifted (dashed line to solid line) according to an external temperature change. As such, when the wavelengths of the oscillation mode 116 and the injection light 120 are shifted, the Fabry-Perot laser 110 may not function as a light source.

As described above, since the conventional wavelength-locked Fabry-Perot laser 110 is sensitive to external temperature change, an additional wavelength stabilization circuit such as a temperature controller (TEC CONTROLER) is required, which is a high economic burden on the subscriber. There is a problem that appears as a result that requires.

The present invention has been made to solve the above-mentioned conventional problems, the object of the present invention is a Fabry-Perot laser device that can ensure a more stable light output than the conventional, even if the external temperature changes, and wavelength division using the same It is to provide a multiple light source.

In order to solve the above problems, the Fabry-Perot laser apparatus having a multiple resonator according to the present invention comprises: a Fabry-Perot laser having first and second reflectors disposed at both ends and forming a first resonator; And a third reflector positioned outside the Fabry-Perot laser and forming a second resonator together with the first reflector.

In addition, the wavelength division multiplex light source connected to the optical transmission link according to the present invention forms an optical waveguide loop, and the light input from the optical waveguide loop is output to an external port, and the light input through the external port. A circulator for cycling on the loop; An optical fiber amplifier disposed on the loop and amplifying the circulating light; Each having a multiple resonator structure, the oscillation modes are densified by magnetic injection light, wavelength-locked by external injection light input from the external port, and outputting wavelength-locked light to the external port; A laser device; A first divider disposed on the loop, for branching a portion of the circulating light and outputting the branched light to the optical transmission link.

1 is a view showing the configuration of a conventional Fabry-Perot laser,

2 to 5 are views for explaining the operating characteristics of the Fabry-Perot laser shown in FIG.

6 is a view showing the configuration of a Fabry-Perot laser device having multiple resonators according to the present invention;

7 to 9 are views for explaining the Fabry-Perot laser device shown in FIG.

10 is a view showing the configuration of a wavelength division multiplex light source using the Fabry-Perot laser device shown in FIG. 6 according to a preferred embodiment of the present invention;

11 to 14 are views for explaining the operation of the wavelength division multiplex light source.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; In describing the present invention, detailed descriptions of related well-known functions and configurations are omitted in order not to obscure the subject matter of the present invention.

6 is a view showing the configuration of a Fabry-Perot laser device having a multiple resonator according to the present invention, Figures 7 to 9 are views for explaining the Fabry-Perot laser device shown in FIG. The Fabry-Perot laser device 200 includes a Fabry-Perot laser 210, a lens 220, and an optical fiber 230.

The Fabry-Perot laser 210 has a first reflector 212 at one end thereof, a second reflector 214 at the other end thereof, and the first and second reflectors 212 and 214 have a first resonator. To form. The first reflector 212 has a relatively high first reflectance, and the second reflector 214 has a relatively low second reflectance.

The lens 220 converges the light 250 emitted from the Fabry-Perot laser 210 to one end of the optical fiber 230, and transmits the light emitted from the optical fiber 230 to the Fabry-Perot laser. Converge to the second reflector 214 of 210.

The optical fiber 230 includes a reflective material 234, and reflects a portion of the optical fiber 230 according to a predetermined third reflectance when the light 250 having a predetermined wavelength is incident on the reflective material 234. The third reflectance of the reflective material 234 is lower than the first reflectance and higher than the second reflectance. The reflective material 234 together with the first reflector 212 forms a second resonator.

7 is a diagram illustrating an oscillation mode spectrum of the first resonator. A plurality of oscillation modes 216 are shown positioned at wavelength intervals depending on the length of the first resonator and the gain characteristics of the material.

8 is a diagram illustrating an oscillation mode spectrum according to a combination of the first and second resonators. Compared to the oscillation mode spectrum shown in FIG. 4A, it can be seen that the oscillation modes 218 are more compact. That is, since the third reflectance is higher than the second reflectance, the oscillation in the second resonator is stronger than the oscillation in the first resonator. As a result, the oscillation modes 218 according to the combination of the first and second resonators are denser than the oscillation modes 216 of the first resonator. When the non-coherent light 240 is injected from the outside of the Fabry-Perot laser device 200, the oscillation modes 218 that do not coincide with the wavelength of the external injection light 240 are suppressed, and the external injection is performed. Light 250 in oscillation mode 218 that matches the wavelength of light 240 is amplified and output. The reflective material 234 magnetically injects the Fabry-Perot laser 210 by reflecting back the coherent light 250 emitted from the Fabry-Perot laser 210 and the external injection light 240 A part of the s) is externally injected into the Fabry-Perot laser 110 by transmitting it according to the third reflectance. The magnetic injection light 250 densifies the oscillation modes 218, and the external injection light 240 is an oscillation mode corresponding to the wavelength of the external injection light 240 among the dense oscillation modes 218. Enhancing 218 induces wavelength locking.

9 illustrates a case in which the oscillation mode spectrum of the Fabry-Perot laser device 200 moves according to an external temperature change. The oscillation mode spectrum of the Fabry-Perot laser device 200 shifts as the external temperature changes, but due to the densification of the oscillation modes 218, the oscillation mode corresponding to the wavelength of the external injection light 240 ( 218 may be present to keep the wavelength locked.

FIG. 10 is a view showing the configuration of a wavelength division multiplex light source using the Fabry-Perot laser device shown in FIG. 6 according to a preferred embodiment of the present invention. The light source functions to output wavelength division multiplexed light to the optical transmission link 440, and includes an optical circulator 310, an optical fiber amplifier 340, a wavelength division multiplexer 430, and The Fabry-Perot laser device 200 and a first splitter 330 are configured.

The optical circulator 330 includes first to third ports, and the light output to the third port is input to the first port through the first splitter 330 and the optical fiber amplifier 340. A path through which the light circulates from the third port to the first port forms an optical waveguide loop 320, and light input to the first port is output to the second port, and input to the second port. The light is output to the third port.

The optical fiber amplifier 340 amplifies the light circulating by being disposed on the loop 320, and includes first to third deflectors 370, 390 and 420, first and second amplifying optical fibers 380 and 410, and a pumping light source. 350, a second divider 360, and a bandpass filter (BPF) 400.

The first and second amplification optical fibers 380 and 410 respectively amplify the circulating light by using induced emission of rare earth elements, and are arranged to be connected in series on the loop 320, and the first and second amplification. Erbium doped fiber (EDF) may be used as the optical fibers 380 and 410.

The pumping light source 350 outputs pumping light of a predetermined wavelength for pumping the first and second amplifying optical fibers 380 and 410, and a laser diode may be used as the pumping light source 350.

The second distributor 360 branches the pumping light partially to couple the first amplifying optical fiber 380, and couples the remaining pumping light to the second amplifying optical fiber 410. Since the second distributor 360 couples the pumping light to the rear ends of the first and second amplifying optical fibers 380 and 410, the first and second amplifying optical fibers 380 and 410 are pumped backward (or reversely pumped). do.

The band pass filter 400 is disposed between the first and second amplifying optical fibers 380 and 410 and has the same bandwidth as the circulating light, thereby amplifying spontaneous emission noise (ASE) outside the bandwidth. remove noise. It is possible to increase the output of the light more efficiently by removing the natural radiation noise and then amplifying the light again.

The first to third deflectors 370, 390, and 420 respectively perform the function of passing the circular light as it is and blocking the light traveling in the opposite direction, and the first splitter 330 and the first light are distributed along the traveling direction of the circular light. Between the first amplifying optical fiber 380, between the first amplifying optical fiber 380 and the band pass filter 400, and between the second amplifying optical fiber 410 and the optical circulator 310. Are placed in turn.

The wavelength division multiplexer 430 is connected to the second port of the optical circulator 310, and has one multiplexing port positioned at one end thereof and N demultiplexing ports positioned at the other end thereof. The wavelength division multiplexer 430 demultiplexes the light input to the multiplexing port and outputs the demultiplexed ports to the demultiplexing ports. do. As the wavelength division multiplexer 430, a waveguide diffraction grating may be used.

Each Fabry-Perot laser 200 is connected to a corresponding demultiplexing port and outputs light having a predetermined wavelength as the wavelength is locked by the demultiplexed light input through the demultiplexing port.

The first splitter 130 is disposed on the loop 120, and splits a part of the multiplexed light output from the third port of the optical circulator 110, and splits the split light into the optical transmission link 260. )

11 to 14 are views for explaining the operation of the wavelength division multiplexing light source. Light of various wavelengths output from the plurality of Fabry-Perot lasers 200 is input to the demultiplexing ports, is spectral divided, and then multiplexed and output. When the wavelength spacing between the light outputs from the plurality of Fabry-Perot lasers 200 is narrower than the channel spacing of the wavelength division multiplexer 430, each of the spectral partitions generated by the wavelength division multiplexer 430 The light exhibits an intensity profile 510 as shown in FIG. The intensity profile 520 represented by the dot islands represents a pass band for each channel of the wavelength division multiplexer 430. Further, the multiplexed light output through the multiplexing port of the wavelength division multiplexer 430 exhibits an output spectrum as shown in FIG. The multiplexed light is input to the optical fiber amplifier 340 after passing through the optical circulator 310 and the first distributor 330. The light passes through the first deflector 370 and is input to the first amplifying optical fiber 380, and the light amplified by the first amplifying optical fiber 380 is output as shown in FIG. 13. It shows the spectrum. The amplified light passes through the second deflector 390 and is input to the band pass filter 400, and the light passing through the band pass filter 400 exhibits an optical spectrum as shown in FIG. 14. . The light input through the band pass filter 400 and input to the second amplifying optical fiber 410 is re-amplified, and the re-amplified high power multiplexed light passes through the optical circulator 310 and then It is input to the wavelength division multiplexer 430 and demultiplexed. Each of the demultiplexed high power light is input to the Fabry-Perot laser 200 to induce wavelength immersion. The wavelength locked light again repeats the above process, and a portion of the multiplexed wavelength locked light is guided to the transmission link 440 by the first splitter 330 and transmitted. The Fabry-Perot laser 200 is directly modulated according to a high speed data signal to be transmitted, thus eliminating the need for an expensive external modulator.

The band pass filter 400 performs a function of suppressing color dispersion effects of light in addition to a function of removing amplified spontaneous emission noise (ASE noise).

As described above, the Fabry-Perot laser device having a multiple resonator according to the present invention has the first and second resonators so that the oscillation modes are densified, thereby matching the wavelength of external injection light even if the external temperature changes. Since the oscillation mode is present, there is an advantage that the wavelength lock can be maintained.

In addition, the wavelength-division multiplexed light source using the Fabry-Perot laser device having the multiple resonator has an advantage that it is possible to ensure a more stable light output than the conventional even if the external temperature changes.

Claims (5)

In a Fabry-Perot laser device, A Fabry-Perot laser disposed at both ends and having first and second reflectors forming a first resonator; And a third reflector positioned outside the Fabry-Perot laser and forming a second resonator with the first reflector. The method of claim 1, Wherein said first and third reflectors have a relatively high reflectance and said second reflector has a relatively low reflectance. The method of claim 1, The Fabry-Perot laser device having a multiple resonator that the third reflector is a reflective material provided in the optical fiber. In a wavelength division multiplexed light source connected to an optical transmission link, A circulator forming an optical waveguide loop, wherein light input from the optical waveguide loop is output to an external port, and light input through the external port is circulated on the loop; An optical fiber amplifier disposed on the loop and amplifying the circulating light; Each having a multiple resonator structure, the oscillation modes are densified by magnetic injection light, wavelength-locked by external injection light input from the external port, and outputting wavelength-locked light to the external port; A laser device; And a first splitter disposed on the loop, for splitting a part of the circulating light and outputting the split light to the optical transmission link. The method of claim 4, wherein the Fabry-Perot laser device, A Fabry-Perot laser disposed at both ends and having first and second reflectors forming a first resonator; Located outside the Fabry-Perot laser, the optical fiber includes a reflective material, The reflective material forms a second resonator together with the first reflector, the first reflector and the reflective material have a relatively high reflectance, and the second reflector has a relatively low reflectance. Multi light source.