Abstract:
Exemplary apparatus and method can be availed for providing at least one electromagnetic radiation. For example, it is possible to provide at least one first electromagnetic radiation having a frequency that changes over time with a first characteristic period. Further, with at least one hardware arrangement, it is possible to receive and modify the first electromagnetic radiation(s) into at least one second electromagnetic radiation having a frequency that changes over time with a second characteristic period. The second characteristic period can be smaller than the first characteristic period. The hardware arrangement(s) can include a resonant cavity having a round-trip propagation time for the first electromagnetic radiation(s) that can be approximately the same as the first characteristic period.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is based upon and claims the benefit of priority from U.S. Patent Application Ser. No.  61 / 548 , 436  filed Oct.  18 ,  2011 , the entire disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    Exemplary embodiments of the present disclosure relate to optics, and more particularly, to apparatus and methods for producing and/or providing optical delays. 
       BACKGROUND INFORMATION 
       [0003]    Recently, a multiple increase in the repetition rate of swept source lasers has been achieved through optical buffering of low duty cycle swept source lasers. In these arrangements, kilometer length and possibly multiple instances of fiber delay lines are typically utilized to achieve the appropriate optical buffering. When implementing buffering schemes greater than  4 ×, the length and number of fiber delay lines can become tedious to implement and difficult to manage. Swept source lasers for OCT imaging have been demonstrated with up to  16 × buffer schemes. (See, e.g., Wolfgang Wieser et al., “Multi-Megahertz OCT: High quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second”, Optics Express, Vol. 18, Issue 14, pp. 14685-14704 (2010)). 
         [0004]    Accordingly, there may be a need to address at least some of the deficiencies described herein above. 
       OBJECTS AND SUMMARY OF EXEMPLARY EMBODIMENTS 
       [0005]    Thus, at least some of the above-described issues and/or deficiencies can be addressed with the exemplary embodiments of the by providing exemplary systems and methods for producing and/or providing optical delays. 
         [0006]    Accordingly, exemplary apparatus and method can be availed for providing at least one electromagnetic radiation. For example, using at least one first hardware arrangement, it is possible to provide at least one first electromagnetic radiation having a frequency that changes over time with a first characteristic period. Further, with at least one second hardware arrangement, it is possible to receive and modify the first electromagnetic radiation(s) into at least one second electromagnetic radiation having a frequency that changes over time with a second characteristic period. The second characteristic period can be smaller than the first characteristic period. The hardware arrangement(s) can include a resonant cavity having a round-trip propagation time for the first electromagnetic radiation(s) that can be approximately the same as the first characteristic period. 
         [0007]    In another exemplary embodiment of the present disclosure, it is possible, using at least one first hardware arrangement, to provide at least one first electromagnetic radiation having a frequency that changes repetitively over time with a first characteristic duty cycle, where the first characteristic duty cycle is less than 0.5. Further, e.g., using at least one second hardware arrangement, it is possible to receive and modify the first electromagnetic radiation(s) into at least one second electromagnetic radiation with a second characteristic duty cycle that is greater than the first characteristic duty cycle. As one example, the first characteristic duty cycle can less than ⅓. The second characteristic duty cycle can be approximately 1. 
         [0008]    According to a further exemplary embodiment of the present disclosure, the second arrangement(s) can include a coupling device which can be configured to admit the first electromagnetic radiation(s), and emit the second electromagnetic radiation(s). The coupling device can be an N×N waveguide device and/or an acousto-optical modulator. The first arrangement(s) can include a source arrangement, and the second arrangement(s) can include a recirculation loop. 
         [0009]    In a further exemplary embodiment of the present disclosure, the second arrangement(s) can further comprise an amplifying device which can be configured to amplify the first electromagnetic radiation(s) and/or the second electromagnetic radiation(s). 
         [0010]    These and other objects, features and advantages of the present invention will become apparent upon reading the following detailed description of embodiments of the disclosure, when taken in conjunction with the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Further objects, features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying drawings showing illustrative embodiments of the present disclosure, in which: 
           [0012]      FIG. 1  is a diagram of an exemplary re-circulating optical buffering arrangement according to an exemplary embodiment of the present disclosure; 
           [0013]      FIG. 2  is a diagram of the exemplary re-circulating optical buffering arrangement according to another exemplary embodiment of the present disclosure; and 
           [0014]      FIG. 3  is a diagram of the exemplary re-circulating optical buffering arrangement according to yet another exemplary embodiment of the present disclosure. 
       
    
    
       [0015]    Throughout the drawings, the same reference numerals and characters, if any and unless otherwise stated, are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the subject disclosure will now be described in detail with reference to the drawings, it is done so in connection with the illustrative embodiments. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the subject disclosure as defined by the appended claims. 
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0016]    According to certain exemplary embodiments of the present disclosure, a re-circulating optical buffering arrangement utilizing a single fiber delay line can be provided. The exemplary re-circulating arrangement can include, e.g., an input port allowing light to be injected into the recirculation loop and an output port allowing light to be extracted at the end of one complete trip inside the loop. According to certain exemplary embodiments of the present disclosure, an 
         [0017]    N×N coupling device can connect the input and output ports to the recirculation loop. The fiber delay line can be connected to the recirculation input and output ports of the N×N coupling device. 
         [0018]    In a particular exemplary embodiment of the present disclosure, the exemplary re-circulating optical buffering arrangement  100  can utilize a single fiber delay line  102 , as shown in  FIG. 1 . The exemplary re-circulating optical buffering arrangement  100  of  FIG. 1  can utilize a 2×2 port 50/50 passive coupler  104  which can be provided to connect input port(s)  106  and output ports  108  to a recirculation loop  110 . According to certain exemplary embodiments of the present disclosure, the light and/or other electro-magnetic radiation injected into the input port  106  can be simultaneously coupled, for example, with approximately a 3 dB loss to the output port  108  and the recirculation loop  110 . The light and/or other electro-magnetic radiation exiting the recirculation loop  110  can be re-coupled into both the output port  108  and the recirculation loop  110  with, for example, an approximate additional 3 dB loss. In certain exemplary embodiments of the present disclosure, a fixed input to output power ratio can be provided that can be incrementally reduced in amplitude with the fixed delay loop cycle. The total recirculation loop path time delay can be chosen, for example, to be equal to the injected light ‘pulse’ width. The pulse can be an impulse or, for example, in the case of a swept source laser, the time for a single sweep. This exemplary re-circulating arrangement can ensure and/or facilitate that the beginning of the delayed light ‘pulse’ coincides with the end of the non-delayed or previous delayed ‘pulse’. 
         [0019]    According to another exemplary embodiment of the present disclosure, an acousto optical modulator (“AOM”)  202 —as a dynamically adjustable coupling device—can be provided in another exemplary re-circulating optical buffering arrangement  200  that is shown, for example, in  FIG. 2 . According to this exemplary embodiment, the light (or other electro-magnetic radiation) injected into an input port  204  can have, for example, multiple (e.g., two) possible paths, such as, e.g., (a) when the AOM  202  is off, the light and/or the electro-magnetic radiation can travel through the AOM  202  with preferably no diffraction, and can enter an output port  206  of the arrangement; and (b) when the AOM  202  is active, the light and/or the electro-magnetic radiation can travel through the AOM  202  with some diffraction efficiency given by the power applied to the AOM  202 , and the non diffracted light can enter the output port  206  of the arrangement while the diffracted light can enter a recirculation loop  208 . The light and/or the electro-magnetic radiation exiting the recirculation loop  208  can also have multiple, (e.g., two) possible paths, such as, e.g., (a) when the AOM  202  is off, the light can travel through the AOM  202  with no diffraction, and can re-enter the recirculation loop  208 ; and (b) when the AOM  202  is active, the light and/or the electro-magnetic radiation can travel through the AOM  202  with some diffraction efficiency given by the power applied to the AOM  202 , and the non diffracted light can enter the recirculation loop  208  while the diffracted light can enter the output port  206  of the exemplary arrangement  200 . 
         [0020]    This exemplary re-circulating arrangement  200  according to the present disclosure can facilitate a dynamically adjustable and optimized input to output power ratios for each fixed delay loop. For example, an initial injection of light and/or the electro-magnetic radiation into the recirculation arrangement ( 200 ) can occur with maximum power applied to the AOM  202 , which can provide the highest diffraction efficiency. This exemplary configuration can facilitate, for example, the majority of light to be injected into the recirculation loop  208 , while the non-diffracted light can enter the output port  206  and can become the non-delayed output. The total exemplary re-circulation loop path time delay can be selected to be equal to (or approximately the same as) the injected light “pulse” width. Where the pulse could be an impulse or, for example, in the case of a swept source laser, the time for a single sweep can be used. This exemplary arrangement  200  can facilitate and/or ensure that the beginning of the delayed light ‘pulse’ coincides with the end of the non-delayed or previous delayed ‘pulse’. 
         [0021]    The exemplary recirculation components and path can be chosen in such a manner to reduce the insertion loss, e.g., the zero order path of the AOM can be utilized. This can maximize the number of achievable loops before the optical power loss is too great for a post buffer booster stage. 
         [0022]    According to yet another exemplary embodiment of the present disclosure, an AOM  302 —as a dynamically adjustable coupling device—can be provided in yet another exemplary re-circulating optical buffering arrangement  300  as shown, for example, in  FIG. 3 . According to this exemplary embodiment, light and/or the electro-magnetic radiation injected into an input port  304  can preferably only enter a recirculation loop  308  when the AOM  302  is active. When the AOM  302  is not active, the light and/or the electro-magnetic radiation preferably travel through the AOM  302  with no diffraction and do not enter any port. In this exemplary arrangement, the injected light and/or the electro-magnetic radiation preferably no longer provide the first non-delayed output. However, this exemplary configuration can provide the lowest insertion loss for the input port to recirculation loop when the AOM  302  is active. The light and/or the electro-magnetic radiation exiting the recirculation loop  308  can have multiple (e.g., two) possible paths, such as, e.g., (a) when the AOM  302  is off, the light can travel through the AOM  302  with no diffraction and can re-enter the recirculation loop  308 ; and (b) when the AOM  302  is active, the light can travel through the AOM  302  with some diffraction efficiency given by the power applied to the AOM  302 , and the non diffracted light and/or the electro-magnetic radiation can enter the recirculation loop  308  while the diffracted light can enter the output port  306  of the exemplary arrangement  300 . 
         [0023]    This exemplary embodiment of the present disclosure can facilitate a dynamically adjustable and optimized input to output power ratios for each fixed delay loop. For example, an initial injection of light into the recirculation arrangement  300  can occur with a maximum power applied to the AOM  302  providing, e.g., the highest diffraction efficiency. This exemplary configuration can facilitate a majority of the light and/or the electro-magnetic radiation to be injected into the recirculation loop  308 , while the non-diffracted light and/or the electro-magnetic radiation can be lost. The total re-circulation loop path time delay can be selected to be equal to, or substantially the same as, the injected light ‘pulse’ width. Where the pulse could be an impulse or, for example, in the case of a swept source laser, the time for a single sweep is provided. This exemplary arrangement  300  can facilitate that the beginning of the delayed light ‘pulse’ coincides with the end of the previous delayed ‘pulse’. 
         [0024]    The foregoing merely illustrates the principles of the present disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. Indeed, the arrangements, systems and methods according to the exemplary embodiments of the present disclosure can be used with and/or implement any OCT system, OFDI system, SD-OCT system or other imaging systems, and for example with those described in International Patent Application PCT/US2004/029148, filed Sep. 8, 2004 which published as International Patent Publication No. WO 2005/047813 on May 26, 2005, U.S. patent application Ser. No. 11/266,779, filed Nov. 2, 2005 which published as U.S. Patent Publication No. 2006/0093276 on May 4, 2006, and U.S. patent application Ser. No. 10/501,276, filed Jul. 9, 2004 which published as U.S. Patent Publication No. 2005/0018201 on Jan. 27, 2005, U.S. Patent Publication No. 2002/0122246, published on May 9, 2002, U.S. Patent Application No. 61/649,546, U.S. patent application Ser. No. 11/625,135, and U.S. Patent Application No. 61/589,083, the disclosures of which are incorporated by reference herein in their entireties. 
         [0025]    It should be understood that the exemplary procedures described herein can be stored on any computer accessible medium, including a hard drive, RAM, ROM, removable disks, CD-ROM, memory sticks, etc., and executed by a processing arrangement and/or computing arrangement which can be and/or include a hardware processors, microprocessor, mini, macro, mainframe, etc., including a plurality and/or combination thereof. In addition, certain terms used in the present disclosure, including the specification, drawings and claims thereof, can be used synonymously in certain instances, including, but not limited to, e.g., data and information. It should be understood that, while these words, and/or other words that can be synonymous to one another, can be used synonymously herein, that there can be instances when such words can be intended to not be used synonymously. Further, to the extent that the prior art knowledge has not been explicitly incorporated by reference herein above, it can be explicitly incorporated herein in its entirety. 
         [0026]    It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements and methods which, although not explicitly shown or described herein, embody the principles of the present disclosure and are thus within the spirit and scope of the present disclosure. Further, various exemplary embodiments described herein can be interchangeably used with all other exemplary described embodiments, as should be understood by those having ordinary skill in the art. In addition, to the extent that the prior art knowledge has not been explicitly incorporated by reference herein above, it is explicitly being incorporated herein in its entirety. All publications referenced herein above are incorporated herein by reference in their entireties.