WO2011024185A2

WO2011024185A2 - A novel modular edfa training kit

Info

Publication number: WO2011024185A2
Application number: PCT/IN2009/000566
Authority: WO
Inventors: Hitesh Mehta; Thomas Lee Sebastial; Yogesh S Shinde
Original assignee: Hitesh Mehta
Priority date: 2009-08-25
Filing date: 2009-10-09
Publication date: 2011-03-03
Also published as: WO2011024185A3

Abstract

The present invention relates to a modular erbium doped fiber amplifier training [EDFA] kit, a modular EDFA training kit specifically designed for providing exposure to various characteristics of EDFA including gain, gain profile signal saturation power, pump saturation power, multiwavelength signal amplification, noise etc. The modular EDFA training kit demonstrating the various EDFA characteristics has plurality modules including amplifier module, a pump module, a wavelength multiplexing module and a wavelength demultiplexing module. Additionally, the modular EDFA training kit may include a microcontroller circuit, a function generator, a digital storage oscilloscope block, a variable optical attenuator block and a multi-meter arranged suitably in a pack with appropriate connections to power supply and to a computer for the purpose of controlling lasers, data recording and/or displaying the results.

Description

A NOVEL MODULAR EDFA TRAINING KIT

FIELD OF INVENTION

[0001] The present invention relates to an erbium doped fiber amplifier [herein after referred to as ΕDFA"] training kit. More specifically, the invention is directed to a modular EDFA training kit for providing demonstration and measurement of EDFA characteristics such as gain, gain profile, signal saturation power, pump saturation power, multiwavelength signal amplification, noise etc. The modular nature aids the student in understanding the building blocks of EDFA. Additionally, EDFA of the EDFA training kit is characterized by variable gain which aids in demonstrating gain dependence on pump and signal power levels and has backward and forward pumping capability which helps in understanding change in gain due to both backward and forward pumping.

BACKGROUND OF THE INVENTION

[0002] Fiber optics has proved to be useful in numerous applications, for example, in transmission of signals in form of voice, video & data, as sensors, as amplifiers [erbium doped optical fiber], as lightguides in medical devices [endoscope] etc.

[0003] In particular, there has been tremendous capacity growth in fiberoptic communications, which permits transmission over longer distances [known as long haul optical transmission] at higher bandwidths [data rates], in comparison to other forms of communications. Fiber optics has replaced metal wires because signals travel along them with less loss, and they are also immune to electromagnetic interference. Fiber optics is one of the significant factors for tremendous development in the field of communication.

[0004] Though the fiber optics has a low transmission loss as compared to the metal wires, in long optical transmission [typically at distances of tens of kilometers or more] the signal transmission loss [referred to as signal losses herein after] accumulates and it becomes inevitable to amplify the signal in the optical fiber.

[0005] The signal losses are compensated by deploying plurality of regenerators (repeaters) and/or optical fiber amplifiers along the optical transmission line in multiple locations, wherein the repeaters and/or the optical fiber amplifiers enhance the signal strength.

[0006] Exemplarily, for systems operating at data rates of GBps, regenerator sites are typically spaced in the range between 35 to 80 Km, depending on the wavelength chosen for transmission, whereas the distance between optical fiber amplifiers may be almost doubled, being in the range from about 80 to 160 km as compared to that with the repeaters.

[0007] Thus, optical fiber amplifiers are preferred in long-distance systems over electrical repeaters because they allow for longer distances between the modules and additionally, the optical fiber amplifier can be easily spliced into the fiber transmission link. Another advantage of optical fiber amplifier being that unlike repeaters they do not require optical/electrical and electrical/optical conversion. [0008] An advantage of the optical fiber amplifier is that they can amplify multiband/multichannel optical signals without de-multiplexing them, thereby avoiding the costs of multiple optical receivers, multiple regeneration circuits and multiple optical transmitters.

[0009] Another advantage that the optical fiber amplifiers provide is that they are capable of amplifying at any bit rate. Thus, even if the transmission rate is greater than before the device is not required to be replaced. One such optical fiber amplifier is the erbium doped optical amplifier based on a length of erbium doped fiber pumped with light of a certain wavelength to amplify the optical signal passing through the amplifier. To use the erbium doped fiber, it is spliced in the fiber optics transmission line at a suitable location.

[00010] Thus, the optical fiber amplifiers and in particular the erbium doped fiber amplifier has many advantages over the electronic repeaters or regenerators.

[00011] Accordingly, a immense deal of study and research in industry and laboratory, for improving the characteristics of the erbium doped fiber and the erbium doped fiber amplifier which include losses, dispersion, noise, networking (WDM), gain, gain flattening etc., is being done globally. Various courses have been designed to teach the basic principles of erbium doped fiber amplifiers, both theoretically and experimentally in numerous colleges and universities.

[00012] It is a universally accepted fact that any concept can only be understood straightforwardly and wholly with help of laboratory experiments. Accordingly, there has been a vast intellectual research to develop students' understanding of the basic concepts of EDFA employing hands-on learning methods, in particular on the experimental part.

[00013] Commercially, numerous devices are available to demonstrate various EDFA characteristics which include losses, dispersion, networking (WDM), gain etc.

[00014] One major disadvantage of these devices available commercially is that they come as a single unit, wherein one or more components are packaged, thus limiting the users (students') access to the details of the components and hence their characteristics.

[00015] Another disadvantage of these devices is that using these instruments only one or at the most two characteristics may be demonstrated.

[00016] Still another disadvantage of these devices is that they are exorbitantly expensive. Though several devices are capable of demonstrating the characteristics of the EDFA, the colleges and/or universities cannot afford to procure these devices for the research, due to exorbitantly high costs.

[00017] In laboratory one may attempt to put up together various components of the EDFA, wherein plurality of EDFA characteristics might be demonstrated. However it is observed that this is unlikely, because it is impossible to assemble and align the multiple EDFA components for performing the experiments or demonstrations, which is tedious, time and energy consuming work. An alternative way to reduce and/or eliminate the tedious, time and energy consuming work is required.

[00018] Additionally, it is desired that the educational/training kit or device capable of demonstrating plurality of EDFA characteristics is economical.

Attempts have been made to design such a training kit or device, wherein it is possible to demonstrate plurality of EDFA characteristics.

[00019] Numerous EDFA training kits are commercially available, wherein it is possible to demonstrate the EDFA characteristics.

[00020] It is observed that the existing EDFA training kits are not capable of providing experiments such as forward and backward pumping, muitiwavelength injection, etc included therein.

[00021] It is also an observation that the features such as use of coarse wavelength division multiplexing [CWDM Mux] and coarse wavelength division de-multiplexing [CWDM De-mux] for filtering out single wavelength of interest, are not provided in the existing EDFA training kits.

[00022] Further, using the existing commercially available EDFA training kits, additional experiments cannot be added. It is desirable that the training kit must be flexible enough so that further components or hardware and software may be added so as to have scope for extending the number of experiments.

[00023] Thus, there exists a need for a training kit for demonstrating the above-mentioned EDFA characteristics, along with being economical, less tedious, less time and energy consuming, compatible for extending or adding additional experiments. Additionally, there exists a need for a training kit wherein the features such as use of coarse wavelength division multiplexing [CWDM

Mux] and coarse wavelength division de-multiplexing [CWDM De-mux] for filtering out single wavelength of interest, EDFA gain, EDFA gain profile etc., are provided.

OBJECTS OF THE INVENTION

[00024] An object of the invention is to provide an EDFA training kit.

[00025] Another object of the invention is to provide a modular EDFA training kit.

[00026] Still another object of the invention is to provide a modular EDFA training kit, wherein the disadvantages associated with the prior art are reduced or eliminated.

[00027] Yet another object of the invention is to provide a modular EDFA training kit, wherein plurality of EDFA characteristics may be demonstrated.

[00028] Another object is to provide a modular EDFA training kit, which is economical.

[00029] Another object is to provide a modular EDFA training kit, wherein it is possible to extend the number of experiments or add or perform experiments or demonstrate the EDFA characteristics.

[00030] Another object is to provide a modular EDFA training kit which reduces or eliminates the need for assembling and aligning the multiple EDFA components for performing the experiments or demonstrations, thus reducing or eliminating the tedious, time and energy consuming work.

[00031] Another object is to provide a modular EDFA, wherein the features such as use of coarse wavelength division multiplexing [CWDM Mux] and coarse wavelength division de-multiplexing [CWDM De-mux] for filtering out single wavelength of interest, EDFA gain, EDFA gain profile etc., are provided.

[00032] The other objects and advantages of the present invention will be apparent from the following description when read in conjunction with the accompanying drawings which are incorporated for illustration of preferred embodiments of the present invention and are not intended to limit the scope thereof.

STATEMENT OF THE INVENTION

[00033] Accordingly the invention provides a modular EDFA training kit specifically designed for providing exposure to various characteristics of EDFA including gain, gain profile, signal saturation power, pump saturation power, multiwavelength signal amplification, noise etc. Additionally, the present invention provides a modular EDFA training kit with features such as use of coarse wavelength division multiplexing [CWDM Mux] and coarse wavelength division de-multiplexing [CWDM De-mux] for filtering out single wavelength of interest,

EDFA gain, EDFA gain profile etc., are provided.

[00034] The various exemplary embodiments of the present invention described herein solves the problems of the prior art and attains the desired objectives with a modular EOFA training kit demonstrating the various EOFA characteristics, wherein the modular EDFA training kit comprises a pump module; an amplifier module; a monitor module; a multiplexing module; a demultiplexing module; a variable optical attenuator; a electronic/electrical module; a plurality of optical cords; and a plurality of electrical cords, wherein the said modules are operationally and suitably connected by means of said optical fiber cords and said electrical cords for demonstration of at least one EDFA characteristics.

[00035] Additionally, the modular EDFA training kit may include a microcontroller circuit, a function generator, a digital storage oscilloscope block, a variable optical attenuator block and a multi-meter arranged suitably in a pack with appropriate connections to power supply and to a computer for the purpose of controlling laser power and its modulation frequency programming, data recording and/or displaying the results.

[00036] The computer and the microcontrollers are suitably programmed for performing various calculations and other details required for demonstrating the EDFA characteristics.

[00037] Using the modular EDFA training kit of the present invention, numerous experiments related to understanding of basic concepts of EDFA may be performed by suitably connecting various modules provided therein.

[00038] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

DETAILED DESCRIPTION OF THE FIGURES

[00039] The detailed description is set forth with reference to the accompanying figures. The use of the same reference numbers in different figures indicates similar or identical items.

[00040] FIG. 1 is a block diagram of a modular EDFA training kit in accordance with one exemplary embodiment of the present invention.

[00041] FIG. 2 is a block diagram of a modular EDFA training kit forward pumping mode.

[00042] FIG 3 is a block diagram of a modular EDFA training kit backward pumping mode.

[00043] FIG 4 illustrates an experimental setup for study of EDFA.

DETAILED DESCRIPTION OF THE INVENTION

[00044] The details disclosed below are provided to describe the following embodiments in a manner sufficient to enable a person skilled in the relevant art to make and use the disclosed embodiments. Several of the details described below, however, may not be necessary to practice certain embodiments of the invention. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect to the following description. In the following section, an exemplary environment that is suitable for practicing various implementations is described.

[00045] This disclosure is directed to an erbium doped fiber amplifier training kit. In particular, the invention is directed to a modular EDFA training kit for providing demonstration and measurement of EDFA characteristics such as gain, gain profile, signal saturation power, pump saturation power, multiwavelength signal amplification, noise etc. The modular nature aids the student in understanding the building blocks of EDFA. Additionally, EDFA of the EDFA training kit is characterized by variable gain which aids in demonstrating gain dependence on pump and signal power levels and has backward and forward pumping capability which helps in understanding change in gain due to both backward and forward pumping.

[00046] FIG. 1 is a block diagram of a modular EDFA training kit in accordance with one exemplary embodiment of the present invention. In accordance with the present invention, the modular EDFA 101 comprises a source [not shown in figure] for input signal 102 that is to be amplified, a pump module 104, a coupler module 103, an amplifier module 105, a filter-isolator module 106, a plurality of photodiodes, a plurality of optical fiber cords, a plurality of electrical cords, a suitable electronic and/or electrical circuits, a computer and a computer program.

[00047] In one embodiment, the modular EDFA training kit 101 comprises a source [not shown in figure] for input signal 102 that is to be amplified, a coupler module 103, a pump module 104, an amplifier module 105, a filter-isolator module 106, a plurality of photodiodes, a plurality of optical fiber cords, a plurality of electrical cords, a suitable electronic and/or electrical circuits, a computer and a computer program, wherein the various modules are suitably connected using the plurality of optical fiber and/or electrical cords and are controlled using the computer program.

[00048] The signal to be amplified 102 in the optical fiber and pump module 104 output are coupled using the coupler module 103, the coupled signal is then fed to the amplifier module 105, which amplifies the signal, and the amplified signal is fed to filter-isolator module 106, wherein the residual pump signal is separated from the amplified signal 107.

[00049] In one embodiment the input signal 102 is the signal to be amplified on the fiber optics transmission line.

n [00050] In one embodiment the coupler module 103 comprises a coarse wavelength division multiplexer, wherein at least two wavelengths may be coupled [multiplexed].

[00051] In one embodiment the coupler module 103 comprises a fiber coupler, wherein at least two wavelengths may be coupled (multiplexed).

[00052] In one embodiment the coupler module 103 is capable of multiplexing wavelengths in range 980 nm and 1525 nm to 1565 nm range.

[00053] In one embodiment the pump module 104 comprises a pump laser.

[00054] In one embodiment the pump module 104 comprises a diode pump laser.

[00055] In one embodiment the pump module 104 comprises a diode pump laser, wherein the pump operates at 980 nm wavelength range.

[00056] In one embodiment the amplifier module 105 comprises a length of erbium doped fiber.

[00057] In one preferred embodiment the amplifier module 105 comprises a length of erbium doped fiber, wherein erbium ions absorb the pump signal and get excited to a higher level, thereby creating a population inversion. The signal to be amplified 102 when propagates through such a population inversion fiber section gets amplified by the process of stimulated emission.

[00058] In one embodiment the length of the erbium doped fiber is from about 10 m to about 20 m. [00059] In one embodiment the filter-isolator 106 module comprises a coarse wavelength division de-multiplexer capable of de-multiplexing [de-coupling] more than two wavelengths.

[00060] In one embodiment the filter-isolator 106 is capable of demultiplexing wavelengths in range 980 nm and 1525 nm to 1565 nm range.

[00061] In one embodiment the modular EDFA may be configured in forward pumping mode. FIG 2 is a block diagram of a modular EDFA training kit in forward pumping mode 201. In accordance with this embodiment the pump signal and the signal to be amplified 202 travels in the same direction as shown in FIG. 2. In order to configure the modular EDFA in forward pumping mode, the pump module 204 is connected to the coupler 203, the coupler being a wavelength division multiplexer, the coupler module 203 is optically connected to the amplifier module 205, which in turn is connected to the filter-isolator module 206, whereas the filter-isolator module 206 is connected to one or more photo- detectors from where the amplified signal 207 emanates.

[00062] In one embodiment the modular EDFA may be configured in backward pumping mode. FIG 3 is a block diagram of a modular EDFA training kit in backward pumping mode 301. In this embodiment the pump signal and the signal to be amplified 302 travels in opposite direction as shown in FIG 3. In order to configure the modular EDFA in backward pumping mode, the pump module 304 is connected to the coupler 306, the coupler being a coarse wavelength division de-multiplexer, whereas the filter-isolator module 306 is connected to one or more photo-detectors (not shown in figure) to which the amplified signal 307 is fed. In this embodiment the coupler module 303 is absent or not needed. The signal to be amplified 302 is directly coupled to the amplifier module 305.

[00063] In one embodiment the photo-detectors are InGaAs PIN photo- detector, capable of detecting wavelengths ranging from about 1525 nm to about 1565 nm and about 980 nm region.

[00064] In one preferred embodiment the modular EDFA training kit is configured in backward pumping mode, wherein the pump signal is avoided from reaching the output detector.

[00065] In one embodiment the modular EOFA training kit includes a microcontroller circuit, a function generator, a digital storage oscilloscope block, a variable optical attenuator block and a multi-meter arranged suitably in a pack with appropriate connections to power supply and to a computer for the purpose of controlling laser power and its modulation frequency programming, data recording and/or displaying the results.

[00066] FIG 4 illustrates an experimental setup for study of EDFA 401, wherein an optical fiber patch cord connects the signal from 1550 nm laser 402c [402a, 402b, 402c and 402d indicate the lasers with wavelengths 1510 nm, 1530 nm, 1550 nm and 1570 nm respectively] to the EDFA module 406 through a variable optical attenuator [VOA] 404, wherein the optical power from the 1550 nm laser is reduced to simulate conditions that are in a fiber optics transmission line, wherein the signal on a fiber optics transmission line is optically attenuated over long distances.

[00067] In accordance with invention, the signal 403 from 1550 nm laser 402d is fed to the VOA 404, which attenuates the signal to result in attenuated signal 405, the attenuated signal 405 is then split into two components to simultaneously monitor input signal power and output power from EDFA, using a 50/50 or 3dB coupler module 406. The split signal 407 is fed to the EDFA module 406, which amplifies the attenuated signal 405 contained in the multiplexed signal 407, with the pump signal creating a state of population inversion in the erbium doped fiber. The output of the EDFA module 408 that is the amplified signal 409 is fed to a photo-detector 411a [which is also referred to as monitor module], whereas the input signal is directed to the photo-detector 411b through the optical connector 410, both of which are connected to the computer 412, wherein data can be recorded and analyzed.

[00068] Numerous sets of observations may be recorded by varying the parameters, namely, signal level, the pump power level and the signal wavelength, wherein one parameter is varied keeping the other two constant.

[00069] In one embodiment the signal wavelength 1550 nm is chosen and the pump power is fixed at 50 mW. The signal power input to the EDFA is varied in suitable steps using the VOA 406 and the resulting output power from the EDFA is measured. A plot of gain versus signal input power reveals the "gain saturation" phenomenon in EDFA. [00070] Thus, connecting the modules suitably and changing one parameter at a time while keeping other parameters constant, various characteristics of

EDFA may be studied using the modular EDFA training kit of the present invention.

[00071] One or more components may be added to the as disclosed EDFA training kit of the present invention to enhance the number of experiments and/or the EDFA characteristics to be studied or demonstrated.

[00072] It is to be noticed that though the present invention has been described with erbium doped optical fiber amplifier, a person skilled in the art recognize that this particular amplifier may be replaced by other types of amplifiers available, for example, Raman amplifiers, the training kit then may be suitably modified to study the characteristics of these amplifiers.

[00073] Thus, the present invention provides a modular EDFA training kit, wherein the disadvantages associated with the prior art are reduced or eliminated, wherein plurality of EDFA characteristics may be demonstrated and is economical.

[00074] Since the EDFA training kit of the present invention is modular in nature it is possible to extend the number of experiments or add or perform experiments or demonstrate the EDFA characteristics.

[00075] Further, the modular nature of the EDFA training kit reduces the need for assembling and aligning the multiple EDFA components for performing the experiments or demonstrations, thus reducing or eliminating the tedious, time and energy consuming work.

[00076] Another advantage of the modular EDFA training kit is that the features such as use of coarse wavelength division multiplexing [CWDM Mux] and coarse wavelength division de-multiplexing [CWDM De-mux] for filtering out single wavelength of interest, are provided.

[00077] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Claims

We claim:-

1. A modular EDFA training kit (101 , 201 , 301) comprising:

a pump module (104, 204, 304); an amplifier module (105, 205, 305); a monitor module (411a, 411b); a multiplexing module (103, 203); a demultiplexing module (106, 206, 306); a variable optical attenuator (404); a electronic/electrical module (412); a plurality of optical cords; and a plurality of electrical cords, wherein the said modules are operationally and suitably connected by means of said optical fiber cords and said electrical cords for demonstration of at least one EDFA characteristics.

2. The modular EDFA training kit of claim 1 , wherein the said pump module (104, 204, 304) comprises a laser of suitable wavelength.

3. The modular EDFA training kit of claim 2, wherein the said laser is a diode laser capable of emitting signal at about 980 nm wavelength region.

4. The modular EDFA training kit of claim 1, wherein the said amplifier module (105, 205, 305) comprises a length of an erbium doped fiber in the range from 10 meters to 20 meters.

5. The modular EDFA training kit of claim 4, wherein the said erbium doped fiber is capable of amplifying the signal in 1525 nm to 1565 nm wavelength region.

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6. The modular EDFA training kit of claim 1 , wherein the said monitor module (411a, 411b) comprises at least a photo-detector capable of detecting the output amplified and the residual pump wavelengths.

7. The modular EDFA training kit of claim 6, wherein the said photo-detector is a InGaAs PIN photo-detector capable of detecting the 980 nm and 1525 nm to 1565 nm wavelengths.

8. The modular EDFA training kit of claim 1, wherein the said multiplexing module (103, 203) comprises an optical coarse wavelength division multiplexer capable of accepting at least two wavelengths at its input and combine them.

9. The modular EDFA training kit of claim 1 , wherein the said de-multiplexing module (106, 206, 306) comprises an optical coarse wavelength division de-multiplexer capable of accepting one input, consisting of different wavelengths combined together and separating (de-multiplexing) them in to single wavelength at each output port.

10. The modular EDFA training kit of claim 1, wherein the said variable optical attenuator (404) is capable of attenuating the optical signal, thereby simulating conditions similar to encountered in fiber optics transmission line.

11.The modular EDFA training kit of claim 1 , wherein the EDFA training kit is configured in forward pumping mode.

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12. The modular EDFA training kit of claim 1, wherein the EDFA training kit is configured in backward pumping mode.

13. The modular EDFA training kit of claim 1, wherein the said plurality of optical cords are optical fiber connector cords.

14. The modular EDFA training kit of claim 1, wherein the said plurality of electrical cords are standard electrical copper connector cords.

15. A modular EDFA training kit as claimed in any of the preceding claims.

16. A modular EDFA training kit as illustrated with the help of accompanying figures.

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