CN1210854C - Variable wavelenght output optic fibre laser - Google Patents

Abstract

The invention relates to a variable wavelength output fiber laser, which mainly includes: a pump source, an optical coupler, a polarization controller, an array waveguide grating, and an optical beam splitter connected in sequence to form a loop. Due to the skillful use of the mature AWG technology in the present invention, the AWG is serially connected in the optical fiber circuit with doped optical fibers, and the AWG is used as an intracavity optical filter to realize the selection of a group of resonance wavelengths and the establishment of amplified radiation. The AWG After multiplexing, the multiplexed end and the pump light are coupled into the doped fiber through the fiber coupler, so that the single pump source can amplify the variable wavelength, simplify the structure of the device, and because of the waveguide integrated structure of the AWG, The size of the device can be reduced, the stability of the device structure can be improved, and light sources with different wavelengths and wavelength intervals can be easily realized by changing the structural parameters of the AWG, and the C-Band and L-Band standard wavelengths and wavelengths of ITU-T can be reliably realized. wavelength interval.

Description

A variable wavelength output fiber laser

technical field

The invention relates to a fiber optic light source, in particular to a fiber optic light source with variable wavelength output, suitable for using amplified spontaneous emission (ASE) light as an auxiliary pump source.

Background technique

Broadband light sources have been studied continuously due to their many applications such as extension to gyroscopic sensors, light sources for testing optical components, and modulated spectra for general access networks. In particular, light sources utilizing ASE light from optical fibers doped with rare earth metals (such as erbium) are relatively good broadband light sources because they exhibit characteristics of wide band, high power, and low loss. For this erbium-doped optical fiber ( All research efforts made by EDF) broadband light sources are about the single band from 1520 to 1560 nanometers, that is, the C-band (C-Band). Most of the existing optical communication components and the traditional erbium-doped fiber amplifier EDFA work in this band. However, with the development of dense wavelength division multiplexing (DWDM--Densed Wavelength Devided Multiples) optical transmission system, the laser light source with variable wavelength output that is simple in structure and easy to realize is of great significance. The multi-channel light source structure can not only realize the Simultaneous output of variable-wavelength lasers, and the purpose of quickly adjusting the wavelength can be easily achieved by selecting channels. However, there is no relatively mature multi-channel variable wavelength output structure at present. The common method is to make single-wavelength (DBR-Distributed Bragg Reflector) lasers or fiber lasers into an array and package them together, which has complex structures and unstable performance. problem, and each wavelength requires a separate drive voltage or temperature control, etc. Recently, tunable lasers based on mode locking have received a lot of attention, but this method has a special limitation on the transmission rate. In recent years, the technology of arrayed waveguide grating (AWG Arrayed Waveguide Grating) has developed rapidly. At the level of commercialization, arrayed waveguide grating AWG can be used as an integrated optical filter array, but it has not been found to apply arrayed waveguide grating AWG to fiber laser.

Contents of the invention

The object of the invention is to provide a variable wavelength output fiber laser that can effectively simplify the structure, reduce the size of the device and improve the structural stability of the device.

In order to realize the purpose of the above invention, the variable wavelength output fiber laser includes a pump source, an optical coupler, a fiber amplifier, a polarization controller, and an optical beam splitter, and is characterized in that it also includes an optical switch and an arrayed waveguide grating, wherein the optical coupler , fiber amplifier, polarization controller, optical switch, arrayed waveguide grating, and optical beam splitter are sequentially connected to form a loop, and part of the light separated by the optical beam splitter is output as an optical signal, and part of the light is returned to the loop as feedback After passing through the optical coupler as an optical input signal, it is continuously amplified by the optical fiber amplifier.

Because the present invention skillfully utilizes the currently mature arrayed waveguide grating (AWG) technology, the arrayed waveguide grating (AWG) is serially connected in the optical fiber circuit with doped optical fiber, and a set of resonance wavelengths can be realized by using the arrayed waveguide grating (AWG) as an intracavity optical filter The selection and establishment of amplified radiation, the connection of the loop of the selected wavelength is realized through the optical switch, and after multiplexing, it is coupled with the pump light into the doped fiber through the fiber coupler, so as to realize the amplification of the light of the selected wavelength and output. When the optical switch connects the channels of different wavelengths, the selection of the wavelength is realized, and the output of the light source with a specific wavelength is established. At the same time, due to the waveguide integration structure of the arrayed waveguide grating AWG, the size of the device can be reduced and the stability of the device structure can be improved. Moreover, since the output light wavelength and the interval between wavelengths are determined by the structure of the arrayed waveguide grating AWG, it is convenient to realize multi-wavelength variable light sources with different wavelengths and wavelength intervals by changing the structural parameters of the arrayed waveguide grating AWG, reliably Realize the C-Band and L-Band standard wavelengths and wavelength intervals of ITU-T, effectively expand the application range of the band of the present invention; and the present invention can also easily realize the adjustment of the output light intensity by adjusting the intensity of the pump light, and The wavelength selection of the light source can be conveniently and easily realized according to whether the corresponding optical paths are connected.

The basic composition and working principle of the present invention are described in detail below in conjunction with accompanying drawing and embodiment:

Description of drawings

Fig. 1 is a structural composition schematic diagram of the present invention;

Fig. 2 is a structural composition schematic diagram of a further embodiment of the present invention;

Fig. 3 is a schematic diagram of the structural composition of the optical switch of the present invention;

Fig. 4 is a structural schematic diagram of the application of the present invention in an optical transmission system;

Detailed ways

As shown in FIG. 1 , the variable wavelength laser provided by the present invention includes a pump source, an optical coupler 1 , a fiber amplifier 2 , a polarization controller 3 , an optical switch 4 , an arrayed waveguide grating 6 , and an optical beam splitter 7 . The pump light generated by the pump source is input from one port of the optical coupler 1, coupled with the part of the output light separated by the optical beam splitter 7 input from the other port of the optical coupler 1, and then output to the fiber amplifier for further processing. Optical amplification, and then polarization adjustment by a polarization controller (PC--Polarization Controller) 3, under the action of the optical switch 4, the polarization-adjusted optical signal can output light of different wavelengths to the Arrayed Waveguide Grating (AWG, Arrayed Waveguide In the different channels 5 of Grating) 6, when a specific wavelength is input to the AWG, the filter tuning of the specific wavelength can be realized through the grating effect of the AWG, and the resonance amplification of the light of the selected wavelength is completed, and finally the beam splitter 7 is used as The output light is output from the laser. Each part of the variable wavelength laser will be described in detail below in conjunction with the accompanying drawings.

As shown in FIG. 1 , the pumping source provides pumping light Pp for the optical coupler 1 . The pumping source is not shown in FIG. 1 , but only the illustration of the pumping light Pp is given. The optical coupler (FC--FiberCoupler) 1 is connected between the pump source and the fiber amplifier 2, couples the pump light and the optical input signal of the pump source together and transmits them to the fiber amplifier 2; Under the excitation of Puguang light, the optical fiber amplifier 2 is used to generate spontaneous radiation light of various wavelengths and directions. In this embodiment, the optical fiber amplifier 2 selects an erbium doped fiber (EDF--Erbium Doped Fiber) amplifier, that is, uses an erbium doped fiber EDF as the Gain medium; due to the gain unevenness of the erbium-doped fiber amplifier, the output optical power of different wavelengths will be different under the same pump power. In order to avoid drastic changes in the output optical power during wavelength switching, the intensity of the output optical power can be adjusted by adjusting the intensity of the pump optical power, or an additional gain as shown in Figure 2 can be added between the fiber amplifier 2 and the polarization controller 3 A flat filter GFF (Gain FlatFilter) 8 is used to achieve gain equalization of light of different wavelengths and improve the gain flat characteristic of the optical fiber amplifier 2 . In addition, in order to prevent the amplification of the EDF from being affected by reflected light and ensure the stable operation of the light source structure, an isolator (Isolator) can be added before and after the optical amplifier, as shown in Figure 1 and Figure 2. A polarization controller (PC—Polarization Controller) 3 is connected behind the fiber amplifier 2, and is used to adjust the polarization state of the spontaneous emission light generated by the fiber amplifier 2.

The optical switch 4 is connected between the polarization controller 3 and the arrayed waveguide grating 6. The structure of the optical switch 4 is shown in FIG. 3, and consists of a 1×N and N×1 optical switch. The optical transceivers before and after the optical switch in Figure 3 are used to represent the input and output of light in order to illustrate the function of the optical switch. In the present invention, it can correspond to the optical amplifier 2 before the optical switch 4 in FIG. 1 and the arrayed waveguide grating (AWG—Arrayed Waveguide Grating) 6 after it. The optical switch is to connect the light of a specific wavelength of the spontaneous emission light after the polarization state adjustment as the input light of the arrayed waveguide grating 6 to the specific wavelength channel 5 of the arrayed waveguide grating 6; wherein there are many ways to realize the optical switch device, and Still in development. The general implementation methods include mechanical, thermo-optic, electro-optic, acousto-optic effects, etc., which can be selected according to the performance requirements. The traditional mechanical switch (such as moving optical fiber) technology is relatively mature, but the response speed is slow. The recently developed micro-electro-mechanical system (MEMS: Micro-electro-mechanical sys terns) optical switch has a faster response speed and a small insertion loss. It can be used as the first choice. The basic principle is to integrate many array surfaces that realize the mirror reflection function on one chip. By adjusting the injection current, the angle of the reflection surface can be changed, thereby changing the transmission direction of light, and outputting the incident light from different outlets. Switch function of optical signal.

Arrayed Waveguide Grating (AWG--Arrayed Waveguide Grating) 6 is suitable as an intracavity optical array filter to realize the selection of a group of resonance wavelengths and the establishment of amplified radiation. The channel 5 of the wavelength λ is connected, so that the filter tuning of a specific wavelength λ can be realized through the grating effect of the AWG, and the resonance amplification of the light of the selected wavelength can be completed. Selectable wavelengths and wavelength intervals are determined by the structure of the AWG.

The beam splitter (BS--Beam Splitter) 7 is connected to the output end of the arrayed waveguide grating AWG6, and is used to divide the light after the arrayed waveguide grating AWG6 multiplexes into two parts, a part of the light is output as an optical output signal, and a part of the light is output as an optical output signal. Feedback returns to the loop as the optical input signal and continues to be amplified through the fiber amplifier 2, where the ratio of output light intensity and feedback light intensity can be realized by adjusting the transmittance and reflectance of the optical beam splitter, so that C-Band or L-Band's erbium-doped fiber amplifier realizes broadband amplification of C-Band or L-Band by a single pump, so that the tuning wavelength can be selected within the range of C-Band or L-Band.

The application of the present invention in dense wavelength division multiplexing (Densed Wavlength Devided Maltipler, DWDM) optical fiber transmission system is shown in Fig. 4. The optical transmission system shown in FIG. 4 includes a multiplexer MUX, an add-drop multiplexer (A/DM), and a cross-connect (XC) device, etc. As a wavelength-variable light source, the present invention can be used as a MUX light source at the transmitting end of an optical transmission system and a channel wavelength protection light source. When a certain channel laser source fails, the variable light source can be adjusted to this wavelength for replacement. Adopting the scheme of the invention does not need to equip each light source with a spare light source, so the spare laser light source can be saved. At the same time, the present invention can be used for the add origination of wavelength add/drop A/DM (Add/Drop) of Optical Add/Drop Multiplex (OADM--Optical Add and Drop Multiplex), to realize flexible add/drop of optical wavelength. In addition, the present invention can also be used in an optical cross-connect (OXC—Optical Cross-Connect) connection module to realize wavelength conversion and solve the problem of wavelength blocking in optical cross-connect.

Claims (3)

1. A variable wavelength output fiber laser, comprising a pump source, an optical coupler (1), an optical fiber amplifier (2), a polarization controller (3), and an optical beam splitter (7), is characterized in that it also includes an optical A switch (4) and an arrayed waveguide grating (6), wherein an optical coupler (1), a fiber amplifier (2), a polarization controller (3), an optical switch (4), an arrayed waveguide grating (6), and an optical beam splitter (7) Connect in order to form a loop, and a part of the light separated by the optical beam splitter (7) is output as an optical signal, and a part of the light is returned to the loop as an optical input signal after passing through the optical coupler (1) as feedback It is further amplified by the fiber amplifier (2). 2. The variable wavelength output fiber laser according to claim 1, characterized in that the fiber amplifier (2) is an erbium-doped fiber amplifier. 3. The variable wavelength output fiber laser according to claim 1 or 2, characterized in that a gain for improving the gain flatness characteristic of the fiber amplifier (2) is provided between the above-mentioned fiber amplifier (2) and the polarization controller (3) Flat filter (8).

Images