1 4 signal router using three Mach-Zehnder interferometers. Sanjeev Kumar Raghuwanshi Ajay Kumar Santosh Kumar

Transcription

1 1 4 signal router using three Mach-Zehnder interferometers Sanjeev Kumar Raghuwanshi Ajay Kumar Santosh Kumar

2 Otical Engineering 5(3), (March 013) 1 4 signal router using three Mach-Zehnder interferometers Sanjeev Kumar Raghuwanshi Ajay Kumar Santosh Kumar Indian School of Mines Deartment of Electronics Engineering Photonics Lab Dhanbad 86004, India santoshrus@ismu.ac.in Abstract. This aer resents an overview of integrated otical signal routing based on the rincile of electro-otic effects. There are some secific tyes of materials whose refractive index changes due to the alication of the electric field. Lithium-niobate (LiNbO 3 ) and gallium arsenide are some imortant electro-otic materials. Due to the alication of the voltage across electrode resent in one of the arms of Mach-Zehnder interferometer (MZI), the electric field changes, hence, hase change in the signal resent in one of the arms. Deending uon the hase change introduced, signal shifts from one waveguide to the other waveguide. Hence, this aer rovides the detailed descrition of 1 4 signal router, using three MZI, and its construction using beam roagation method. Finally, the results are verified by the MATLAB-based results. 013 Society of Photo-Otical Instrumentation Engineers (SPIE) [DOI: /1.OE ] Subject terms: signal router; Mach-Zehnder interometer; linear waveguide; S-bend sine waveguide; beam roagation method. Paer received Dec. 8, 01; revised manuscrit received Jan. 8, 013; acceted for ublication Feb. 4, 013; ublished online Mar. 4, Introduction Curvilinear directional coulers, branching and combining waveguides, S-shaed bend waveguides, and taered waveguides are indisensable comonents in constructing an integrated otical circuit. In ractical directional coulers, however, light couling in the S-shaed bend waveguide regions, in the front and rear of arallel waveguides, should be taken into account in order to evaluate the roagation characteristics recisely. Otical interferometer circuits, comosed of otical coulers and otical delay arts, are a basic element emloyed in various otical devices. 1 3 Such circuits include Mach-Zehnder interferometers (MZIs), lattice-form filters (or cascaded MZIs), transversal-form filters, and interferometers with ring resonator filters. 4 8 Treyz 9 showed the silicon Mach-Zehnder waveguide interferometers oerating at wavelength 1.3 μm. This resented the switching mechanism based on the thermally induced variation of the refractive index of crystalline silicon. Besse et. al. exlained about the otical switches based on Mach- Zehnder configuration with imroved extinction ratios. 10 They study driving conditions to imrove the extinction ratios in and 1 all-otical switches based on semiconductor otical amlifiers in Mach-Zehnder configuration. Hu et al. used symmetric and asymmetric Y-branches, emloying height-taered waveguides, in order to achieve ower slitting and mode sorting, resectively, in the interferometer. 11 Yoshimoto et al. roosed the olarization-insensitive MZI switch that is useful for otical gate elements. 1 This is esecially well suited to wavelength-division multilexing network comonents. Lagali et. al. roosed the generalized MZIs for variable ratio ower slitting and otimized switching. 13 They analyzed the nonideal integrated otical N N generalized MZI (GMZI) emloying multimode interference (MMI) coulers using the transfer matrix technique. Schreieck et al. resents the results of /013/$ SPIE cross-gain and cross-hase modulation exeriments on InGaAsP-based semiconductor otical amlifiers and MZI switches. 14 Tol et al. resents an MZI-based low-loss combiner. 15 They have shown a nonlinear MZI to rovide the combiner function without control signals and nonlinear effect caused by carrier deletion in the semiconductor otical amlifiers (SOAs). Zheng et al. introduced the threedimensional (3-D) mode roagation analysis and oint matching method which resents a novel formulation technique to analyze the low- and high-frequency characteristics for the imedance-matched olymer MZI electro-otic (EO) switch based on MMI coulers. 16 Mizuno et al. resented a theoretical and exerimental study of an otical interferometer circuit with a uniform wavelength sacing. 17 Kumar et al. roosed a simle all-otical logic device, called MZI, which is comosed by using an SOA and an otical couler. 18 Raghuwanshi et al. 19 studied the Y-branch having inbuilt otical slitters and combiner using beam roagation method (BPM). 19 This aer outlines the design rocess of a signal router based on integrated three MZIs. An EO switch is a device used in integrated fiber otics. The device is based on MZI and is made by titanium diffusion in lithium niobate substrate. The switching between the orts is achieved by an EO effect within the structure. Voltage, alied to the electrodes deosited on the integrated MZI, creates an electric field distribution within the substrate which, consequently, changes its refractive index. If roerly designed, the induced change, in the refractive index, leads to different couling between individual orts. In Sec., we exlain about the EO effect. Section 3 exlains about the formation of signal router and Sec. 4 resents and discusses the results obtained from BPM and MATLAB. Electro-Otic Effect Switches and coulers fall in the categories of integrated otical devices. In fact, as the name suggests, the devices, which can be fabricated on a wafer, are known as integrated Otical Engineering March 013/Vol. 5(3)

3 otical devices. Essentially, we are creating the light guiding environment on the substrate so the circuit, essentially, looks like an integrated circuit. That is why it is given the name integrated device. In this aer, we are creating a waveguide structure on a substrate and sending the signal from otical fiber to these devices. The roerty of light is changed, then the light is launched back again into an otical fiber. At the heart of the integrated otical devices, a henomenon called the EO effect occurs. Refractive index of the material changes with alication of electric field. Lithium-niobate (high degree of loss but high EO coefficient) and gallium arsenide (low EO coefficient) are some imortant EO materials. The change in the refractive index is given by the L8-Integrated Otics-I. video in Ref. 0. n 3 Δn ¼ re; (1) where r is EO coefficient and E is the electric field. We have certain materials whose dielectric constant can be changed by the alication of an electric field or magnetic field. If we consider a material that changes the dielectric constant due to an alication of electromagnetic field across it, then those tyes of material are called EO material. If the dielectric constant changes due to the alication of magnetic field, then those tyes of material are known as magneto-otic materials. Here, we want to make use of EO material and the effect that the dielectric material changes by the alication of electric field is called EO effect. Gallium arsenide required high electric field to realize the same changes as in lithium niobate; however, there is less loss when this material is used. Basically, lithium niobate is an anisotroic material; therefore, the refractive index and dielectric constant remain different in different directions when the electric field is alied. In short, we can say that, we have the material in which the refractive index can change with the alication of electric field. This effect is also known as the Pockel effect. The Pockel effect states that the refractive index changes roortional to the alied electric field. Now, by using the roerty of the material, we essentially can alter the characteristics of the light assing through the material and we can write the hase changes due to the alied electric field as 0 Δφ ¼ ðδnþl: () λ Now, from Eq. (1), we can write Δφ ¼ n 3 re L: (3) λ For a given device, and for an otical signal, λ is constant and n is a constant refractive index of the substrate material. The EO coefficient of the material is constant. Therefore, essentially, we have the roduct of E and L. If we use the high value of the electric field, the length required remains reasonably small, but the change in the refractive index is very small. The change in the refractive index is tyically So to get a substantial hase change into the light, we require a significant length for the roagation of Table 1 Different arameters to obtain articular voltage V. Wavelength (λ) Searation between the electrode (d) Value of arameters 1.33 μm 6 μm Refractive index 1.47 Electro-otic coefficient Substantial length (L) m V 10,000 μm light. Hence, it is immediately clear that since Δn is very small, we require a length, tyically of the order of a few millimeters, to obtain the substantial hase change in the light outut. When the ga between the electrodes is reduced, electric field is increased and the size of the device is reduced to a few millimeters in length in order to get the substantial change in the hase of the device. These arameters are shown in Table 1. Let us say, if the voltage difference between these two electrodes is V and d is the searation between the electrodes, then electric field will be aroximately V d. Hence, we can write Δφ ¼ n 3 V λ d r L: (4) Therefore, when no voltage is alied, Δφ remains zero, and when we aly the voltage ðvþ the hase is changed by. This articular voltage is known as V. Hence, we can write V ¼ λ 1 d n 3 r L : (5) To get the corresonding value of V, we require substantial length L. d cannot be reduced significantly. If we try to reduce d, then electric field will be artly inside and outside; consequently, field strength might be larger than the breakdown field. Searation cannot be less than a few microns. Essentially, d cannot be decreased to get the value V. Therefore, there is limitation on all these quantities. Thus, for substantial length V, voltage remains very low. So, this is basic for a module which works on the rincile of EO effect and the hase of the signal which can be changed by the alication of the signal voltage across the channel waveguide as the frequency of the signal increases. Due to the alication of the electric field, the hase difference changes and, hence, couling length of the device changes due to which signal shifts in the other waveguide. 3 Formation of the Signal Router The idea of MZI is very simle. Here, we show the lan on lithium niobate. We have a substrate, which is lithium niobate, and above the substrate, we have created the channel waveguide as shown in Fig. 1. The device contains two inut orts and two outut signal orts associated with electrode, so that can change the refractive index of one of the arms. Light is brought and we have two-way ower divider so that the light gets equally divided into two arts, roagates in the arms, and again combines. It requires equal combiner Otical Engineering March 013/Vol. 5(3)

4 Fig. 1 Basic schematic view of Mach-Zehnder interferometer with roer electrode. and finally signal gets combined and slits into two orts using a signal slitter. 19 Assuming that the two have exactly identical aths, the signal reaches in hase, so whatever signal is given in inut, the same signal can be obtained at the outut. Let us now say that we ut an electrode around this. Therefore, we have created a hase modulator around one of the arms of this MZI. Now, we can aly the voltage across the electrode. So, when zero voltage is alied to one of the arms, in this case, constructive interference takes lace. When the voltage is alied, destructive interference takes lace. Now, the signal is allowed to ass through the 3-dB couler. So, on the basis of hase difference introduced on the two arms the signals are divided on the two outut orts; we can aly the same concet in order to obtain the signal router or de-multilexers. We can write the equation as follows: A ¼ ffiffiffiffiffiffiffiffiffiffiffiffi 1 α 1 ðe in Þþj ffiffiffiffiffi α 1ð0Þ; (6) B ¼ j ffiffiffiffiffi α 1ðEin Þþ ffiffiffiffiffiffiffiffiffiffiffiffi 1 α 1 ð0þ; (7) where α 1 is attenuation constant of first directional couler reresented toward the inut side of Fig. 1. In matrix form, it can be reresented as follows: A ¼ B ffiffiffiffiffiffiffiffiffiffiffiffi 1 α 1 j ffiffiffiffiffi α 1 Similarly, we can write j ffiffiffiffiffi ffiffiffiffiffiffiffiffiffiffiffiffi α 1 Ein : (8) 1 α 1 0 C ¼ Ae jφ 1 (9) D ¼ Be jφ : (10) C D In matrix form, we can write e jφ 1 0 A ¼ 0 e jφ B. (11) In the case of second couler, we can write the equation as follows: OUT 1 ¼ ffiffiffiffiffiffiffiffiffiffiffiffi 1 α ðcþþj ffiffiffiffiffi α ðdþ (1) OUT ¼ j ffiffiffiffiffi ffiffiffiffiffiffiffiffiffiffiffiffi α ðcþþ 1 α ðdþ: (13) In Eqs. (10) and (11), α reresents the attenuation constant of the second directional couler, reresented toward the outut side of Fig. 1. We can reresent Eqs. (10) and (11) in matrix form as follows: ffiffiffiffiffiffiffiffiffiffiffiffi OUT1 1 α ¼ OUT j ffiffiffiffiffi α j ffiffiffiffiffi α C ffiffiffiffiffiffiffiffiffiffiffiffi. (14) 1 α D Now utting the values of C, D, A, and B from Eqs. (8) and (11) in Eq. (14), we get ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi OUT 1 ¼½ 1 α 1 1 α e jφ ffiffiffiffiffiffiffiffiffiffi 1 α 1 α e jφ ŠEin (15) ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi OUT ¼ j½ α 1 1 α e jφ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 þ α 1 α 1 e jφ ŠEin : (16) In order to achieve the highest extinction ratio α 1 ¼ α ¼ 0.5. In this case, the extinction ratio can be reresented as the ratio of the maximum and the minimum ower levels of the transfer function. Hence, if the minimum ower level of the transfer function is zero, we have the infinite extinction ratio. Basically, to achieve the highest extinction ratio, we require 50% of the ower slitting ratio for otical coulers. Hence, ideally, the coulers used in Otical Engineering March 013/Vol. 5(3)

5 designing the device must have the attenuation constants 0.5. Hence, we can write P out1 ¼ OUT 1 Δφ ¼ je jðφ0þ sin ¼ sin Δφ E in (19) OUT 1 ¼ 1 ½e jφ 1 e jφ ŠEin : After simlification, we can write Δφ OUT 1 ¼ je jðφ0þ sin E in : (17) In the same manner, we can write OUT ¼ j 1 ½e jφ 1 þ e jφ Š Δφ OUT ¼ je jðφ0þ cos E in ; (18) where we assume that φ 1þφ ¼ φ 0, and φ 1 φ ¼ Δ φ. Now, normalized ower at ort 1 and ort can be reresented as follows: P out ¼ OUT Δφ E ¼ je jðφ0þ cos ¼ cos Δφ : (0) in Here, φ 1 and φ are the hase differences that arise due to alication of the voltage across the electrode, where φ 1 ¼ V V 1 and φ ¼ V V. Hence, deending uon the hase difference, signal shifts from one ort to another ort. By using this configuration, we can make the signal router. The block diagram of the signal router is given in Fig.. This block diagram is a combination of the three MZIs. Each MZI is caable of switching the signal on the second waveguide deending uon the voltage given at the electrode. Figure 3 shows the combination of three MZIs. The two oututs, obtained from the first MZI, are connected to the inut of the second and third MZI. Now, by alying the voltage at electrode of each MZI, we can either kee the signal in the same arm or shift the signal into the other Fig. Block diagram of a signal router using three Mach-Zehnder interferometers. Fig. 3 Signal router using three Mach-Zehnder interferometers. Otical Engineering March 013/Vol. 5(3)

6 arm deending uon the alied voltage. In this rocess, we have grounded electrode 1 and electrode 3. Basically, due to alication of roer voltage (V ¼ 6.75 V) for the alied arameter and ath length, the signal remains in the same waveguide. Various arameters are shown in Table 1 to obtain articular voltage ðv Þ, hence we obtained the value of V as 6.75 V. Similarly, when no otential difference is alied across electrode, signal shifts into the second waveguide. These exlanations can be roven using Eqs. (19) and (0). Hence, by alying the aroriate control signal, which is nothing but the otential alied at electrode of each MZI, we can select any outut ort among the four outut orts. Therefore, the system can be used as a signal router. Here, crystal material is lithium niobate and its roagation direction is in Y direction. The waveguides of MZI are created by the diffusion Reference index Wavelength Polarization Table Simulation arameters. Modal 1.3 μm Transverse magnetic Mesh-number of oints 500 BPM solver Engine Paraxial Finite difference Scheme arameter 0.5 Proagation ste 1.3 Boundary condition Transarent boundary condition (TBC) of titanium in lithium niobate substrate. Width of waveguide is 8 microns and material used for waveguide is TiLiNbO 3. We have secified an electrode region with three electrodes, all with zero voltage, ositioned slightly off the symmetry axis of the MZI. Table shows the different simulation arameters. Now, the same structure is created twice in order to obtain the structure of signal router. 4 Results and Discussion Finally, we used the BPM by alying the various combinations of the control signal (the voltage at the electrode of each MZI, keeing other two electrodes grounded of each MZI). Now, with the alication of the various control signals, the oututs are shown in Fig. 4. Figure 4 shows the travelling of the inut signal u to various orts deending uon the choice of the control signal s 1, s, and s 3. Figure 4(a) shows that inut signal aroaches toward outut ort 1 as we have alied control signal s 1 ¼ 6.75 V, s ¼ X (can be 6.75 Vor 0 V), and s 3 ¼ 0V. We can see that, due to alication of the control signal s 1 ¼ 6.75 V, the signal exists in the same waveguide as the hase difference is. However, due to alication of the control signal s 3 ¼ 0, shift of the signal from one arm to the second arm takes lace, and, finally, whole signal aears on outut ort 1. Similarly, we can select the outut ort by making the choice s 1 ¼ 6.75 V, s ¼ X, and s 3 ¼ 6.75 V as shown in Fig. 4(b). Hence, by making the choice s 3 ¼ 6.75 V, we can introduce the hase shift of in the third MZI. Therefore, the signal exists in the same arm of the third MZI and outut ort can be selected. By alying the same concet, we can obtain the outut at outut ort 3 and outut ort 4, resectively. We can reresent the combination of the control signals s 1, s, and s 3 for obtaining the outut at the various orts in Table 3, where X is considered as don t care (either 6.75 V or 0 V). We can generate the above result, using MATLAB, by alying the roer mathematical exression. From Fig. 4, Fig. 4 The otical field roagation at various outut orts deending uon the control signal s 1 ;s, and s 3, where s 1 ;s, and s 3 are the voltage alied at the second electrode of first, second, and third MZI. (a) Outut signal at ort 1 for control signal s 1 ¼ 6.75 V, s ¼ X (can be 6.75 V or 0 V), and s 3 ¼ 0 V. (b) Outut signal at ort for the control signal s 1 ¼ 6.75 V, s ¼ X, and s 3 ¼ 6.75 V. (c) Outut signal at ort 3 for the control signal s 1 ¼ 0 V, s ¼ 6.75 V, and s 3 ¼ X. (d) Outut signal at ort 4 for the control signal s 1 ¼ 0 V, s ¼ 0 V, and s 3 ¼ X, where X is treated as don t care conditions. Otical Engineering March 013/Vol. 5(3)

7 Table 3 The outut ower at the four outut orts on the basis of control signal s 1, s, and s 3. s 1 s s 3 ort1 Outut_ Outut_ ort Outut_ ort3 Outut_ ort V X 0 V V X 6.75 V V 6.75 V X V 0V X Table 4 Various arameters for Δϕ 1, Δϕ, Δϕ 3. we can write the mathematical exression for the normalized outut ower at the orts 1,, 3, and 4 as follows: P out1 ¼ cos Δφ3 sin Δφ1 ; (1) when s 1 ¼ 6.75 V; s ¼ X; and s 3 ¼ 0V P out ¼ sin Δφ3 sin Δφ1 ; when s 1 ¼ 6.75 V; s ¼ X; and s 3 ¼ 6.75 V P out3 ¼ sin Δφ cos Δφ1 ; when s 1 ¼ 0V; s ¼ 6.75 V; and s 3 ¼ X () (3) for getting the outut signal at PORT 1 for getting the outut signal at PORT for getting the outut signal at PORT 3 for getting the outut signal at PORT 4 P out4 ¼ sin Δφ sin Δφ1 ; when s 1 ¼ 0V; s ¼ 0V; and s 3 ¼ X. (4) V V 6.75 V 0 V 0 V V 0 V 0 V 6.75 V 0 V V 3 0 V 6.75 V 0 V 6.75 V Δϕ 1 Δϕ Δϕ 3 V ðv 1 V Þ V ðv Þ V ðv 3 V Þ V ðv 1 V Þ V ðv Þ V ðv 3 V Þ V ðv 1 V 3 Þ V ðv V 3 Þ V ðv 3Þ V ðv 1 V Þ V ðv Þ V ðv 3 V Þ Table 4 shows the various arameters for Δϕ 1, Δϕ, Δϕ 3. Figures 5 to 8 show the MATLAB lots of the normalized outut ower at orts 1,, 3, and 4. Figure 5 shows the stewise variation in normalized outut ower, at orts 1,, 3, and 4, due to the alication of the control signal s 1 ¼ 6.75 V, s ¼ X, and s 3 ¼ 0V. Finally, the outut exists at ort 1 only on the voltage s 1 ¼ 6.75 V. Similarly, Fig. 6 shows the stewise variation in normalized outut ower, at orts 1,, 3, and 4, due to the alication of the control signal s 1 ¼ 6.75 V, s ¼ X, and s 3 ¼ 6.75 V. Figure 7 shows the outut ower at ort 3 exists on the Fig. 5 The variation of the outut ower at orts 1,, 3, and 4 due to the variation in control signal s 1 (alied control signals are s 1 ¼ 6.75 V, s ¼ X, and s 3 ¼ 0 V). Otical Engineering March 013/Vol. 5(3)

8 Fig. 6 The variation of the outut ower at orts 1,, 3, and 4 due to the variation in control signal (alied control signals are s 1 ¼ 6.75 V, s ¼ X, and s 3 ¼ 6.75 V. Fig. 7 The variation of the outut ower at orts 1,, 3, and 4 due to the variation in control signal s (alied control signals are s 1 ¼ 0 V, s ¼ 6.75 V, and s 3 ¼ X ). voltage signal s 1 ¼ 0V, s ¼ 6.75 V, and s 3 ¼ X. In the same manner, Fig. 8 shows the result of the outut ower at ort 4. 5 Conclusion We have designed the 1 4 signal router by the combination of the three MZIs. The switching between the orts can be achieved by an EO effect within such tye of structure. Voltage, alied to the electrodes deosited on the integrated MZI, creates an electric field distribution within the substrate which, consequently, changes its refractive index. Due to variation of the refractive index, hase difference arises; hence, deending uon the hase, signals shift from one waveguide to another waveguide. Using this concet, we have imlemented the signal router and run the BPM simulation to find out the otimum values of the electrode Otical Engineering March 013/Vol. 5(3)

9 Fig. 8 The variation of the outut ower at orts 1,, 3, and 4 due to the variation in control signal s 3 (alied control signals are s 1 ¼ 0 V, s ¼ 0 V and s 3 ¼ X ). voltages. Our BPM results have been exactly matched by MATLAB-based simulation results. Acknowledgments The authors would like to acknowledge Indian School of Mines, Dhanbad for financial suort for conducting the resent research work. References 1. L. F. Stokes, M. Chodorow, and H. J. Shaw, All-single-mode fiber resonator, Ot. Lett. 7(6), (198).. B. Moslehi et al., Fiber-otic lattice signal rocessing, Proc. IEEE 7(7), (1984). 3. K. P. Jackson, G. Xiao, and H. J. Shaw, Coherent otical fibre delayline rocessor, Electron. Lett. (5), (1986). 4. N. Takato et al., Silica-based integrated otic Mach Zehnder multi/ demultilexer family with channel sacing of nm, IEEE J. Sel. Areas Commun. 8(6), (1990). 5. C. Kostrzewa and K. Petermann, Bandwidth otimization of otical add/dro multilexers using cascaded coulers and Mach Zehnder sections, IEEE Photon. Technol. Lett. 7(8), (1995). 6. Y. Zhao et al., Simlified otical millimeter-wave generation configuration by frequency quadruling using two cascaded Mach Zehnder modulators, Ot. Lett. 34(1), (009). 7. C. C. Wang, High-frequency narrow-band single-mode fiber-otic transversal filters, J. Lightw. Technol. 5(1), (1987). 8. K. Oda et al., A wide-band guided-wave eriodic multi/demultilexer with a ring resonator for otical FDM transmission systems, J. Lightw. Technol. 6(6), (1988). 9. G. V. Treyz, Silicon Mach-Zehnder waveguide interferometers oerating at 1.3 μm, Electro. Lett. 7(), (1991). 10. P. A. Besse and H. Melchior, All-otical switches based on Mach- Zehnder configuration with imroved extinction ratios, IEEE Photo. Technol. Lett. 9(1), (1997). 11. M. H. Hu et al., Tunable Mach Zehnder olarization slitter using height-taered Y-branches, IEEE Photo. Technol. Lett. 9(6), (1997). 1. N. Yoshimoto et al., High-inut-ower saturation roerties of a olarization-insensitive semiconductor Mach Zehnder interferometer gate switch for WDM alications, IEEE Photo. Technol. Lett. 10(4), (1998). 13. N. S. Lagali et al., Analysis of generalized Mach-Zehnder interferometers for variable ratio ower slitting and otimized switching, J. Lightwave Technol. 17(1), (1999). 14. R. Schreieck et al., Ultrafast switching dynamics of Mach Zehnder interferometer switches, IEEE Photo. Technol. Lett. 13(6), (001). 15. J. J. G.M. vander Tol, H. de Waardt, and Y. Liu, A Mach Zehnderinterferometer-based low-loss combiner, IEEE Photo. Technol. Lett. 13(11), (001). 16. C. T. Zheng et al., Investigation on ush ull olymer Mach-Zehnder interferometer electro-otic switches using imroved 3-D mode roagation analysis method, Ot. Quant. Electron. 4(5), (011). 17. T. Mizuno et al., Uniform wavelength sacing Mach-Zehnder interferometer using hase-generating coulers, J. Lightwave Technol. 4(8), (006). 18. S. Kumar, I. B. Pauria, and A. Singhal, Otical fiber communication system erformance using MZI switching, Int. J. Soft Comut. Eng. (3), (01). 19. S.K.Raghuwanshi et al., Proagation study of Y-branch having inbuilt otical slitters and combiner using beam roagation method, in Progress in Electromagnetics Research Sym. Proc., (01). 0. R. K. Shevgaonkar, Seakfirst, L8-Integrated Otics-I [Video], (011), htt://ntel.iitm.ac.in/courses/ /8 (5 November 01). Sanjeev Kumar Raghuwanshi is an assistant rofessor at Electronics Engineering Deartment of Indian School of Mines, Dhanbad. He is working in the area of otical fiber communication. He received a PhD degree in the field of fiber otics from the Deartment of Electrical Communication Engineering of I.I.Sc. Bangalore, India, in 009. He has also authored a book titled Contemorary Otical Fiber Technology ublished by Agrawal Publication, Agra, India, in 011. He has also contributed one chater in Otical Network: Current Issue and Review ublished by IGI Global, USA. He has imlemented one roject on modeling of wavelength-division multilexing otical comonents finance by Indian School of Mines, Dhanbad. He has ublished over 30 research aers in reuted national and international journals and resented about 40 research aers in different national and international conferences, including IEEE. He is a member of IEEE. Currently, he is guiding five PhD students. He is faculty in charge of electronics engineering, Indian School of Mines, Dhanbad. Otical Engineering March 013/Vol. 5(3)

10 Ajay Kumar received a bachelor s degree in electronics and instrumentation engineering from National Institute of Science and Technology, Berhamur, Orissa, India, and a master s degree in electronics and communication engineering from Indian School of Mines, Dhanbad, India. He is ursuing his PhD degree from the Deartment of Electronics Engineering, Indian School of Mines, Dhanbad, under the guidance of Dr. S. K. Raghuwanshi. He is working in the area of otical fiber communication. He is a graduate member of the Institute of Electrical and Electronics Engineers. He is receiving the MHRD scholarshi for his PhD from the Indian School of Mines, Dhanbad. Santosh Kumar received a bachelor s degree in electronics and communication from the Marathwada Institute of Technology, Aurangabad, Maharashtra. He is ursuing his PhD degree from the Deartment of Electronics Engineering, Indian School of Mines, Dhanbad under the guidance of Dr. S. K. Raghuwanshi. He is working in the area of otical fiber communication. His research interest is inhomogeneous/non-uniform otical waveguides. He has ublished aers in reuted journals as well as in conferences, including the IEEE. He is receiving the full scholarshi for his PhD research from the Indian School of Mines, Dhanbad. He is a graduate member of the IEEE. He is also a member of SPIE. Otical Engineering March 013/Vol. 5(3)