in the following the details of various preferred embodiments of the present invention are disclosed . the preferred embodiments are described with the aid of the accompanying drawings , wherein like reference numerals refer to like elements throughout . [ 0034 ] fig7 a through 7c are diagrams illustrating the methodology of spectrum division multiplexing ( sdm ) and the operation of a versatile interleaver , referred to herein as an optical spectrum synthesizer ( oss ), according to embodiments of the present invention . moreover , hereinafter , the terms “ spectrum filter ”, “ asymmetric interleaver ”, “ 1 / n interleaver ”, “ spectrum splitter ” are used interchangeably to describe various embodiments of the present invention . in fig7 a , a systematical way of organizing a collection of signal channels into smaller groups is disclosed . in the particular example illustrated in fig7 a , sixteen signal channels are divided into four groups of channels , referred to herein as four spectra . moreover , hereinafter , the terms “ spectrum ”, and “ spectra ” are used interchangeably with “ group of signal channels ”, and “ groups of signal channels ” to describe various embodiments of the present invention . in fig7 b , an oss preferably has two outputs . one output has a group of broader periodic pass bands with a predetermined bandwidth and period as depicted in fig7 c . the other output has a group of narrower periodic pass bands , which complements that of output 1 . the labels of output 1 and 2 are not critical and the outputs can also be labeled as n and b for narrow and broad output . when the bandwidth of the n output is set to be identical to that of the output b , the device becomes a conventional interleaver as displayed in fig3 a through 3d . referring now to fig8 a , a preferred embodiment of an oss ( 800 ) comprises a 50 % broadband non - polarizing beam splitter ( 803 ) and two nano - t gt mirrors ( 805 and 807 ). the thickness of each optical cavity of the nano - t gt mirrors is predetermined to obtain desired output spectra with proper channel spacing and / or wavelength separation . the incoming light ( 802 ), preferably a parallel beam with a small angular divergence , is directed to the beam splitter ( 803 ) at a predetermined incident angle with respect to the surface normal of 803 . the branched beam then enters two nano - t gt mirrors where upon exiting , the phases of the light beams are modified . the two light beams are then recombined and re - branched to form two outputs . these input and output light beams are interfaced / coupled to optical fibers through lenses . a preferred type of lens is a graded index lens known as a grin lens . in one preferred embodiment , the reflective surfaces of the nano - t gt mirrors have reflectivities of approximately 18 %, and 99 . 5 % respectively . in order to match the center frequencies of the pass bands of output 1 and 2 to that of a standard communication grid ( e . g ., itu grid ), the incident angles and / or environment temperature ( s ) of the oss are adjusted . in addition , one or both of the optical cavities may be constructed with piezoelectric materials such that the free - spectra - range of each of the optical cavities may be controlled . another preferred way to adjust the free - spectra - range of the “ air - spaced ” gt mirror is to set and control the gas mixture and the pressure of the “ air - spaced ” cavity . the temperature environment may also be controlled in a way to enhance the performance of the oss . one or more electrical heaters and coolers are placed close ( within a few decimeters ) to the two optical cavities to ensure best performance . the temperature sensitivity of the etalon can be reduced by using material with low thermal expansion . temperature is important because typically a 1 degree c . change in temperature can have an effect on the critical product of width and index of refraction comparable to the required precision to achieve the desired outputs . referring now to fig8 b , a preferred embodiment of a modified oss ( 810 ) comprises a 50 % broadband non - polarizing beam splitter ( 813 ), two nano - t gt mirrors ( 815 and 817 ). the thickness of each optical cavity of the nano - t gt mirrors is predetermined to obtain desired output spectra with proper channel spacing and / or wavelength separation . two incoming light beams ( 811 , 812 ), preferably parallel beams with small angular divergences , are directed to the beam splitter ( 813 ) at predetermined incident angles with respect to the surface normal . the branched beams then enter two nano - t gt mirrors where upon exiting , the phase of the light beams are modified . the two light beams are then recombined and re - branched to form two outputs . these input and output light beams are interfaced / coupled to optical fibers through lenses . a preferred type of lens is a graded index lens known as a grin lens . in one preferred embodiment , the reflective surfaces of the nano - t gt mirrors have reflectivities of approximately 18 %, and 99 . 5 % respectively . in order to match the center frequencies of the pass bands of output 1 and 2 to that of a standard communication grid ( e . g ., itu grid ), the incident angles and / or environment temperature ( s ) of the oss are adjusted . in addition , one or both of the optical cavities may be constructed with piezoelectric materials such that the free - spectra - range of each of the optical cavities may be controlled . another preferred way to adjust the free - spectra - range of the “ air - spaced ” gt mirror is to set and control the gas mixture and the pressure of the “ air - spaced ” cavity . the temperature environment may also be controlled in a way to enhance the performance of the oss . one or more electrical heaters and coolers are placed close ( within a few decimeters ) to the two optical cavities to ensure best performance . the temperature sensitivity of the gt mirrors can be reduced by using material with low thermal expansion . temperature is important because typically a 1 degree c . change in temperature can have an effect on the critical product of width and index of refraction comparable to the required precision to achieve the desired outputs . referring now to fig8 c , a preferred embodiment of a modified oss ( 820 ) comprises a 50 % broadband non - polarizing beam splitter ( 823 ) and two nano - t gt mirrors ( 825 and 827 ). the thickness of each optical cavity of the nano - t gt mirrors is predetermined to obtain desired output spectra with proper channel spacing and / or wavelength separation . two incoming light beams ( 821 , 822 ), preferably parallel beams with small angular divergences , are directed to the beam splitter ( 823 ) at predetermined incident angles with respect to the surface normal . the branched beams then enter two nano - t gt mirrors where upon exiting , the phase of the light beams are modified . the two light beams are then recombined and re - branched to form two outputs 824 and 826 . these input and output light beams are interfaced / coupled to optical fibers through lenses . a preferred type of lens is a graded index lens known as a grin lens . in one preferred embodiment , the reflective surfaces of the nano - t gt mirrors have reflectivities of approximately 18 %, and 99 . 5 % respectively . in order to match the center frequencies of the passing bands of output 1 and 2 to that of a standard communication grid ( e . g ., itu grid ), the incident angles and / or environment temperature ( s ) of the oss are adjusted . in addition , one or both of the optical cavities may be constructed with piezoelectric materials such that the free - spectra - range of each of the optical cavities may be controlled . another preferred way to adjust the free - spectra - range of the “ air - spaced ” gt mirror is to set and control the gas mixture and the pressure of the “ air - spaced ” cavity . the temperature environment may also be controlled in a way to enhance the performance of the oss . one or more electrical heaters and coolers are placed close ( within a few decimeters ) to the two optical cavities to ensure best performance . the temperature sensitivity of the gt mirrors can be reduced by using material with low thermal expansion . temperature is important because typically a 1 degree c . change in temperature can have an effect on the critical product of width and index of refraction comparable to the required precision to achieve the desired outputs . referring now to fig9 a , the modified oss disclosed above may be used to exchange a portion of the signal channels based upon another preferred embodiment 900 of the present invention . a periodic passband contained in input signal 1 ( 901 ) will be directed to outputi ( 904 ) whereas the complementary periodic passband will be directed to output 2 ( 906 ). for signal channels contained in input signal 2 ( 902 ), the corresponding periodic passbands will be directed to output 1 and 2 , to fill the vacated regions of the full spectra . the net effect is that the two spectra contained in inputs 1 and 2 are exchanged at the outputs 1 and 2 . referring now to fig9 b , the modified oss disclosed above may also be used to perform add / drop function in a single step according to a preferred embodiment 910 of the present invention . a periodic passband contained in input signal ( 912 ) will be dropped to outputl ( 914 ) whereas the complementary periodic passband will be directed to output ( 916 ). the added signal channels are sent through the spectrum add port ( 911 ). these periodic passbands will be directed to the output ( 916 ) fiber . in fig1 a , an oss preferably has two outputs . one output has a group of broader periodic pass bands with a predetermined bandwidth and period as depicted in fig1 b . the other output has a group of narrower periodic pass bands , which complements that of output 1 . the labels of output 1 and 2 are not critical and the output can be better labeled as n and b outputs . when the bandwidth of the n output is set to be identical to that of b , the device becomes a symmetrical interleaver as displayed in fig3 a through 3d . in a preferred embodiment , a phase correction element and spectrum filter element may also be introduced to each output to enhance the oss performance . in a preferred embodiment of the present invention , one of the outputs is used to carry channels with one oc protocol , e . g ., oc - 192 , the other output is used to carry channels of a different oc protocol to best utilize the frequency space and maximize the data throughput rate . in a different embodiment of the present invention , different oc protocols may be carried in one or both of the outputs . [ 0046 ] fig1 a is a diagram illustrating a one to four spectrum de - multiplexer ( sdemux ) constructed with three oss devices . in a preferred embodiment of the present invention , three oss devices are in a cascade with appropriate spectrum filters and / or phase correction elements to form a sdemux . in a preferred embodiment of the present invention , the optical spectrum is evenly divided into four complementary spectra with the same pass channel bandwidths . in a different preferred embodiment of the present invention , the optical spectrum is divided into four complementary spectra having different pass channel bandwidths . in another preferred embodiment of the present invention , the number of the optical spectra or output groups , n , is greater than one . when n is equal to two , the sdemux is simply an oss , whereas when n is equal to four , the sdemux device is as illustrated in fig1 a . in additional embodiments of the present invention , a particular sdemux can be used in the reverse direction as a smux . in these cases , n different and complementary spectra are combined through a smux to form a single composite output signal . fig1 b illustrates a proposed symbol 1100 for a sdemux . referring now to fig1 a through 12b , a group of three 1 / 3 demux and a group of three 1 / 3 mux are illustrated , respectively . according to a preferred embodiment of the present invention , n 1 / n demux devices and n 1 / n mux devices are constructed for a sdemux or smux device . each 1 / n demux ( and 1 / n mux ) carries a subgroup consisting of 1 / n of the total number of channels . in a different preferred embodiment of the present invention , each 1 / n demux ( and 1 / n mux ) carries a spectrum , which uses a fraction of the whole frequency space , and in certain cases this fraction may be set to 1 / n . the 1 / n demux inputs 1201 , 1222 and 1242 produce outputs 1204 , 1224 and 1244 , respectively . the 1 / n mux inputs 1212 , 1232 and 1252 produce outputs 1214 , 1234 and 1254 , respectively . [ 0048 ] fig1 a is a diagram illustrating a long haul system according to a preferred embodiment 1300 of the present invention wherein grouped input signals 1362 , 1372 , 1382 and 1392 are transported to grouped output signals 1364 , 1374 , 1384 and 1394 . in this case , a long haul system is formed using a sdemux 1304 , n optical fibers 1310 , 1320 , 1330 and 1340 , edfas ( erbium doped fiber amplifiers ) and a smux 1306 . due to a much larger channel spacing compared with a conventional long haul system using only one optical fiber or several optical fibers with broadband filters , nonlinear effects are significantly reduced . a much higher optical power can therefore be lunched into each of the n fibers thereby significantly increasing the distances between amplification and / or recondition stations . fig1 b is a diagram illustrating a long haul system according to a preferred embodiment of the present invention . in this case , a long haul system is assembled using n 1 / n - mux , n optical fibers 1360 , 1370 , 1380 and 1390 , edfas and n 1 / n - demux devices . due to a much larger channel spacing compared with a conventional system using fewer optical fibers , nonlinear effects are significantly reduced . a much higher optical power can therefore be launched into each of the n fibers thereby significantly increasing the distances between amplification and / or recondition stations . in a different embodiment of the present invention , a combination of conventional dwdm devices , smux , sdemux , 1 / n mux , 1 / n demux and edfa devices are arranged in a way to achieve a long haul transport system consisting of more than one fiber to transport the composed signal spectrum with a larger channel spacing in each of the fibers . referring now to fig1 a , 14b and 14 c , an optical spectrum add - drop module ( osad ) 1400 is assembled using two oss based upon a preferred embodiment of the present invention . a group of signal channels can be added and removed simultaneously . this device can be used to direct network data traffic in a collective way . in another preferred embodiment of the present invention , the status of many channels can be monitored using a sadm in a parallel way to speed up network data management and routing . fig1 b depicts a proposed symbol for this new device and fig1 c illustrates a long haul implementation using the sadm . input spectrum signal 1402 has spectrum signal 1406 dropped and spectrum signal 1408 added to produce output spectrum signal 1404 in fig1 a and 14b . in fig1 c , input spectrum signals 1453 are combined in smux 1454 with input spectrum signals 1432 from 1 / 4 mux 1430 . the dropped spectrum signals 1448 via 1 / 4 demux 1440 and leave output spectrum signals 1458 at sdemux 1456 . [ 0051 ] fig1 a and 15b disclose a preferred construction of a 1 × 4 spectrum switch ( ss ). in this case , a 4 × 4 optical switch 1520 follows an sdemux 1510 that allows flexible redirection of subgroups of signal channels 1508 . in other preferred embodiments , lxn ss is constructed with the combination of 1 to n sdemux and an nxn optical switch . fig1 b illustrates a proposed symbol for the spectrum switch 1500 . referring now to fig1 , a 4 × 4 × 4 spectrum cross - connect ( scc ) 1600 is disclosed . the construction of this scc has a similar structure in comparison with a conventional optical cross - connect where different channels in a conventional cross connect are replaced by subgroups of channels in a scc . according to a preferred embodiment of the present invention , eight 1 × 4 ss are connected to form this scc . a general n × n × m scc uses 2 n 1 × m ss connected in a way similar to a conventional n × n × m optical cross connect . inputs 1 - 4 ( 1601 , 1602 , 1603 and 1604 ) are cross connected to become outputs 1 - 4 ( 1605 , 1606 , 1607 and 1608 ). [ 0053 ] fig1 a and 17b are diagrams illustrating a module 1700 and spectra for which overlapping spectra input 1702 are passed as the outputs 1714 , 1716 , 1724 and 1726 , according to a preferred embodiment of the present invention . a wavelength insensitive branch coupler is used to branch the original composed data into two or several parts . an oss is then used to split the composed signal into two spectra . these spectra are used in a collective way to process and pass data at a higher throughput rate than conventional methods by allowing certain degrees of crosstalk between adjacent channels . the crosstalk between adjacent channels is then removed through electronic and / or optical decoding of the original data . in another preferred embodiment of the present invention , a spectrum processor 1800 is disclosed where a flexible usage of the frequency space is enabled . as illustrated in fig1 a , the frequency space is divided to accommodate different oc protocols as well as to provide a group of channels all within a specific frequency window and with a different channel spacing and width . such a sp module can be made with a combination of oss 1810 , 1820 and 1830 and filters 1814 , 1824 , 1834 and 1840 as illustrated in fig1 a generating the spectra of fig1 b . having thus disclosed various embodiments of the present invention , it being understood that numerous alternative embodiments are contemplated and that the scope of the invention is limited only by the appended claims and their equivalents , what is claimed is :