Communications

Riza and his group’s contributions in the field of communications include pioneering works in RF wireless communications, optical wireless communications and fiber-optic communications.

Riza is a pioneer in the use of MEMS for fiber-optic switching (SPIE 1992, US Patent 1993). In the fiber-optic signal attenuation arena, the group has pioneered the most diverse set of variable optical attenuator (VOA) modules using optical MEMS, Acousto-Optic (AO), liquid and Liquid Crystal (LC) technologies (IEEE 1998). Riza invented the fault-tolerant all-digital paradigm for designing fiber-optic signal power conditioning and routing modules that include multi-wavelength equalizer modules (OSA 1999). This technique provides 100% repeatable and energy efficient controls for light flow controls in fiber communications. Riza pioneered the design  of fiber-optic signal conditioning and routing modules using the reliable Texas Instruments (TI) Digital Light Processing (DLP) technology, namely using the Digital Micromirror Device (DMD). The group for example proposed and demonstrated using the DMD, the world’s first fault-tolerant variable attenuators, all-digital fiber-optic switches, spectral equalizers, tunable laser designs and wavelength sensitive add-drop filters. Riza also invented the Hybrid MEMS/LC design for fiber-optic applications including the hybrid analog-digital design for producing world record performance VOAs (IEEE 2005). Other Riza inventions include super low noise LC switches and low loss MEMS, LC, and hybrid MEMS-LC 3-D cross-connect switches. Specifically, Riza invented the world’s first N x N large port count crossconnect design using 3-D beamforming optics that allowed inherent light power attenuation control at localized fiber ports and also proposed and demonstrated the exceptionally low near zero coupling loss fiber-to-freespace-to-fiber connection designs such as using the self-imaging fiber-to-free-space-to-fiber design (IEEE 1998, US Patent 2000, SPIE 2000 and 2003, OSA 1999 and 2003). These methods have been deployed and extended in commercially deployed fiber-optic modules including the very large crossconnect optical circuit switches (e.g., Calient Technologies) that are performing ultra-low loss optical circuit switching operations  in many data centers around the world with over 750,000 deployed fiber terminations. It is important to note that Riza’s near zero coupling loss fiber-to-freespace-fiber self-imaging designs reduced optical power losses with over an order of magnitude impact and in fact, with larger freespace propagation distance between fibers such as needed in crossconnect circuit switches, created many orders of magnitude reduction in optical losses. Thus vital energy savings occurred with such low loss Fiber-optic signal controls designs enabling acceleration and development of the modern internet for the world high bandwidth data communications. In effect, greener and wide spread operations for the internet data services were possible as the energy saved due to lower loss optical designs was energy well spent elsewhere such as in fiber-optical amplifiers that require additional pump laser energy to boost data signals in the fiber transmission lines typically placed every 40 km. Thus the Riza low losss designs also created in-direct and critical impact for the overall infrastructure of the growing and evolving internet.

Many of the Riza’s fiber-optical design inventions underwent prototyping and commercialization at Nuonics, Inc., a 1998 startup company founded by Riza. The Nuonics design technology underwent acquisition and sale to a global commercial corporation. This DMD-based design technology and its extension is deployed in many commercialized products (e.g., Newport Corp., Cidra Corp., Nistica Corp/NTT Electronics/Fujikura/Molex) such as fiber-optic multiwavelength equalizers and routers across the world fiber-optic communications and internet infrastructure.

In 1992, Riza & his GE colleagues pioneered spatial optical CDMA, a space division multiplexing (space MUX) method to transmit multiple simultaneous data channels, both for optical wireless and multi-fiber bundle optical data communications (SPIE 1992). The method combined space-time coding to realize a multiaccess optical network. A decade later, many efforts evolved around the world to deploy Space Mux in few mode fiber and multicore fiber to increase data carrying capacity of fiber networks. Realizing that coupling freespace interconnected light between single mode fibers (SMFs) can be a challenge, Riza in 1994 proposed the first use of a variable focus lens for SMF fed optical wireless short range interconnects (IoP 1994) and later extended the work to incorporate 3-D beamforming for robust SMF-freespace-to-SMF coupling controls (SPIE 1997).

Continuing with the same theme of SMF-freespace coupling, the group also developed the most advanced theoretical models for freespace-to-SMF lens coupling (OSA 1999, 2003) that has realized near zero loss SMF-to-freespace-to-SMF optical power transfer for short distances as well as for longer range optical wireless link distances (Elsevier 2006), including the use of smart optical 3-D beamforming combining cascaded strong and weak lensing via the self-imaging mechanism to form ultra-low loss point-to-point optical datacom links as well as for low loss optical wireless power transfer (IEEE 2012, US Patent Appl. 2014). These smart 3-D beamforming works have been incorporated around the world to maximize received link optical power for adequate signal-to-noise (SNR) to set optical wireless data transmission records for terrestrial, indoor and underwater links as well as highly efficient optical wireless power transfer links.

In his 1995 SPIE Proceedings paper, Riza extended his mm-wave RF multibeam multi-user beamforming approach to the optical wireless application, creating the first use of multiple simultaneous beams for multiple users using  electronically programmable beamforming optics such as liquid crystal phased array optical devices.

Riza introduced and demonstrated the first smart indoor multiple beams optical wireless concept (IEEE 1999) using agile 3-D optical beamforming-based reconfigurable light (for both laser and LED light) to produce  both Line of Sight (LOS) and Non Line of Sight (NLOS) (SPIE 2013) robust and high efficiency indoor optical wireless communications, including its first application for data centers (JEOS 2011, IEEE 2012). Others around the world have used the Riza multibeam reconfigurable indoor optical wireless system to set world indoor optical wireless data records for eye safe telecom C-band operations and develop systems for IEEE Industry 4.0 Standard. In addition, designers have used the Riza lab SMF-freespace ultra-low loss coupling models and techniques to commercially deploy millions of SMF-freespace/solid optic-based components that are deployed across the world optical communications and internet infrastructure.

In the free-space optical wireless domain, Riza invented Multiplexed Optical Scanner Technology (MOST), a new powerful method using polarization (P-MOS), space (S-MOS), wavelength (W-MOS), and code (C-MOS) multiplexing, including hybrid mux-methods to realize no-moving parts three dimensional steering of light for optical wireless and imaging applications (IEEE 1999). These optical scanners set world records for large aperture 4-pi steradian coverage inertia less optical scanning (OSA 2004). Riza also invented the first de-centered variable focus electronically controlled lens including MEMS lens and liquid lens-based optical beam steering method (SPIE OE 2004, Elsevier 2009) and combined it with liquid lens focus/defocus methods to make smart search and lock-in low loss optical wireless data links (JEOS 2011) as well as fiber-optic attenuation and switching components (Elsevier 2000, 2009, 2010). In 2018, Riza introduced his newest invention, the camceiver, the world’s first combined camera plus data transceiver module with applications in data centers and indoor user ID tag locating systems (IEEE 2018). The camceiver features full spectrum UV to SWIR operations including designs for T/R operations with high speed fiber-optic data links.

Riza is also a pioneer in multiple simultaneous RF beams optical beamforming systems for RF wireless communications phased array antennas and his 1989 Caltech Ph.D. work proposed such smart beamforming systems. In particular, in 1995, he was the first to propose the use of optical multi-beamforming systems for RF wireless Base-Station antennas for cellular systems including for mm-wave (today called 5G and 6G) high data rate wireless phased array antennas on a variety of fixed and mobile platforms including automobiles (SPIE 1995). He proposed the first design for frequency reuse and smart frequency allocations within a cell using spatially multiplexed antenna beams via a multi-beams optical beamformer. In addition, in the same 1995 SPIE paper to improve multi-user wireless data transfer performance, he proposed the first design combining the use of carrier/sub-carrier frequency multiplexing and spatial multiplexing of multiple simultaneous beams for RF cellular base-station phased array antennas (PAA). This approach was much like the 1996 proposed Orthogonal Frequency Division Multiplexing-Multiple Input Multiple Output (OFDM-MIMO) or spatial-spectral multiplexing MIMO PAA method that today is an IEEE standard for RF wireless communications.  Several world labs have pursued both the combined frequency-space Multiplexing multi-beam PAA idea as well use of optical controls approach for mm-wave wireless communication array antennas.

As mentioned earlier, Riza also proposed these multi-beamforming techniques for the optical wireless regime, effectively, pioneering Spatial Multiplexing via Optical Multi-beamforming and Spatial-Frequency Multiplexing for both the RF mm-wave and optical wireless domains of multi-access communications.

— Multi-beam RF (mm-wave/5G) Communications including use of Spatial Multiplexing and Combined Spatial- Frequency Multiplexing in Array Antennas

Journal and Conference Publications:

1. N. A. Riza, “An acoustooptic-phased-array antenna beamformer for multiple simultaneous beam generation,” IEEE Photonics Technology Letters, 4.7, 807-809, 1992.
2. N. A. Riza, “Optical multiple beam-forming systems for wireless communication antennas,” SPIE Conf. on Wireless Communications, Vol. 2556, pp. 139-150, Sept. 1995.
3. N. A. Riza, S. A. Khan, M. A. Arain, “Flexible beamforming for optically controlled phased array antennas,” Optics Communications, Vol.227, pp.301-310, 2003.
4. N. A. Riza, “ High Speed Multi-Beamforming for Wideband Phased Arrays,” IEEE Microwave Photonics (MWP) Topical Meeting Proc., pp. 405-409, Sept. 2003.
5. N. A. Riza, “Fault-Tolerant Multi-Beam Photonic Beamforming for Wideband Array Antennas,” SPIE Photonics North Conference, SPIE Proc. Vol. 5260, pp. 62-73, May 26-29, Montreal, Canada, 2003.
6. N. A. Riza, “Smart Optical Beamforming for Next Generation Wireless Empowered Communications, Power Transfer, Sensing and Displays: Building on the Past,” IEEE ISSC Conference Proc. paper, June 9-10, Cork, Ireland, 2022.

— Optical Wireless (Free-space Optical Communications including Spatial Optical CDMA or Optical Space Division Multiplexing & Spatial Multiplexing of Optical Wireless Beams and 3-D beam-steering methods)

Journal Publications:

1.     N. A. Riza, J. E. Hershey, and A.  A. Hassan “A signaling system for multiple access laser communications and interference protection” Applied Optics ,  Vol. 32, No. 11, pp. 1965-1972, April 10, 1993.

2.  A. Hassan, J. E. Hershey, and N. A. Riza, “Spatial Optical CDMA,” IEEE Journal on Selected Areas of Communications, Vol.13, No.3, pp.609-613, April 1995.

3.     N. A. Riza and S. Sumriddetchkajorn, “Fault-tolerant variable fiber-optic attenuator using three dimensional beam spoiling,” Elsevier J. of Optics Communications, Vo.185, 103-108, Nov.1, 2000.

4. Z. Yaqoob, A. A. Rizvi and N. A. Riza, “Free-space wavelength multiplexed optical scanner,” Applied Optics, 40(35), 6425-6438, Dec. 10 (2001).

5.     Z. Yaqoob and N. A. Riza, “Free-Space Wavelength-Multiplexed Optical Scanner Demonstration,” Applied Optics-IP, Vol. 41, Issue 26, Page 5568 (September 2002).

6.     N. A. Riza and Muzamil A. Arain, “ Code multiplexed optical scanner,” Applied Optics, IP, Vo.42, No.8, March 10, 2003.

7.     N. A. Riza and S. A. Khan, “ Polarization multiplexed optical scanner,” Optics Letters, Vol.28, No.7, pp.561-163, April 1, 2003.

8.     Z. Yaqoob, M. Arain, N. A. Riza, “ Wavelength multiplexed optical scanner using photothermorefractive glasses, Applied Optics-IP, Vol. 42, No. 26, p. 5251, Sept. 2003.

9.     Z. Yaqoob and N. A. Riza, “Low loss wavelength-multiplexed optical scanners using volume Bragg gratings for transmit-receive lasercom systems,” Optical Engineering, Vol.43, No.5, pp.1128-1135, May 2004.

10.     N. A. Riza and M. A. Arain, “Super Wide Angle Coverage  Code Multiplexed Optical Scanner”, Optics Letters, Vol.29, No.9, pp.1004-1006, May 1, 2004.

11.     N. A. Riza and Z. Yaqoob, “Space Multiplexed Optical Scanner,” Applied Optics, Vol.43, No.13, pp.2703-2708, 1 May 2004.

12.  S. A. Khan and N. A. Riza, “Demonstration of 3-dimensional wide angle laser beam scanner using liquid crystals,” Opt. Express 12, 868-882, 2004.

13. M. J. Mughal and N. A. Riza, “Variable fiber-optic attenuator using bulk micromachined deformable micromirror,” SPIE J. Optical Engineering (OE), Vol.43, Oct.10 2004. (De-centered MEMS E-lens freespace beamsteering)

14.  N. A. Riza and S. A. Khan, “Ultra-low loss laser communications technique using smart beamforming optics,” Optics Communications, Vol. 257, Issue 2, pp. 225-246, 15 January 2006.

15.  N. A. Riza and S. A. Khan, Erratum to “Ultra-low loss laser communications technique using smart beamforming optics” [Opt. Commun. 257 (2) (2006) 225–246], Optics Communications, Vol. 259, Issue 2, pp.888-890, 15 March 2006.

16.  S. A. Reza and N. A. Riza, “A Liquid Lens-Based Broadband Variable Fiber Optical Attenuator,” Elsevier J. Optics Communications, Vol. 282, No.7, pp.1298-1303, April 2009. (De-centered Liquid lens freespace beam steering)

17. N. A. Riza and P. J. Marraccini, “Broadband 2×2 Free-Space Optical Switch Using Electrically Controlled Liquid Lenses,” Optics Communications, Vol.283, pp.1711-1714, 2010. (De-centered Liquid lens freespace beam steering)

18.  P. J. Marraccini and N. A. Riza, “ Power Smart In-door Optical Wireless Link Design,” online Journal of the European Optical Society (JEOS) Rapid Publications, Vol.6, 11054,  Dec.02, 2011.

19.  P. J. Marraccini and N. A. Riza, “Smart multiple-mode indoor optical wireless design and multimode light source smart energy-efficient links,” SPIE Optical Engineering Journal, Vol.52, 5, May 2013.

Conference Publications:

1.     N. A. Riza, J. E. Hershey, and A.  A. Hassan “Novel multi-dimensional coding scheme for multi-access optical communications,” Multigigabit Fiber Communications OE/Fibers Conference  Proceedings of  SPIE, Vol. 1790, pp.110-120, 1992.

2.     N. A. Riza and M. C. DeJule, “A Novel Programmable Liquid Crystal Lens Device for Adaptive Optical Interconnect and Beamforming Applications,” Optical Computing Int.Conf., Edinburgh, IoP Publishing, pp.231-234, Aug. 22-25, 1994.

3.     N. A. Riza, “Optical Multiple Beamforming Systems for Wireless Communication Antennas,” SPIE Conference Proceeding  on Wireless Communications, Vol.2556, pp. 139-150, July 1995.

4.     N. A. Riza, “Multichannel Variable Optical Control Systems for Large Coherent Optical Arrays,” SPIE Proc, pp.333-337,  Orlando, April, 1996.

5.     N. A. Riza, “Switchboard in the sky:freespace optics platform for communications and processing,” IEEE LEOS Ann. Mtgs. Digest, Dec., 1998.

6.     N. A. Riza and Y. Huang, “High Speed Optical Scanner for Multi-Dimensional Beam Pointing and Acquisition,” IEEE-LEOS Annual Meeting, San Francisco, CA, Nov. 1999.

7.     N. A. Riza, “Reconfigurable Optical Wireless,” IEEE-LEOS Annual Meeting, San Francisco, CA, Nov. 1999.

8.     Z. Yaqoob and N. A. Riza, “Agile Optical Beam Scanner using Wavelength and Space Manipulations,” 46th Annual Symposium on Optical Science and Technology, San Diego, California USA, SPIE Proc. 4471, pp. 262-271, August 2001

9.     Z. Yaqoob, J. Steedle, and N. A. Riza, “Wide Angle High Speed Large Aperture Optical Scanner,” in IEEE LEOS 14th Annual Meeting, San Diego, CA, Vol. 2, pp. 616-617, Nov. 2001

10.  N.A. Riza, Guest Editor Special Issue of the SPIE Optical Processing Working Group NewsLetter on the Topic “Freespace Optical Wireless,”  October 2001.

11.  Z. Yaqoob and N. A. Riza, “ 2pi sterradian coverage transmit-receive lasercom system using smart multiplexing of multiplexed optical scanners,” Freespace laser communications and Laser Imaging II, 47th Annual SPIE Meeting, 7-11 July, Seattle, Washington, USA, 2002.

12.  S. A. Khan and N. A. Riza, “Polarized Multiplexed Optical Scanner,” in IEEE LEOS 15th Annual Meeting, Glasgow, Nov. 2002.

13.  M. A. Arain and N. A. Riza, “Code Multiplexed Optical Scanner,” in IEEE LEOS 15th Annual Meeting, Glasgow, Nov. 2002.

14.  Z. Yaqoob and N. A. Riza, “Microseconds Speed Wavelength Multiplexed Optical Scanner,” in IEEE LEOS 15th Annual Meeting, Glasgow, Nov. 2002.

15.  Z. Yaqoob and N. A. Riza, “ Low-loss wavelength-multiplexed optical scanner using volume Bragg gratings for broadband transmit-receive lasercom systems,” SPIE Conference on Free-Space Laser Communication and Active Laser Illumination III, SPIE Proc. Vol. 5160, No. 47,  6 Aug 2003, San Diego, CA USA.

16.  S. A. Khan and N. A. Riza, “High-speed polarization multiplexed optical scanner for three-dimensional scanning applications,” SPIE Conference on Free-Space Laser Communication and Active Laser Illumination III, SPIE Proc. Vol. 5160, No. 26,  5 Aug 2003, San Diego, CA USA.

17.  M. A. Arain and N. A. Riza, “Optical transceiver using Code-Multiplexed Optical Scanner,” IEEE LEOS Ann. Mtgs. Digest, Paper MA2,  Oct.27, 2003.

18.  M. A. Arain and N. A. Riza, “Free Space Optical Wireless using Code-Multiplexed Optical Scanner”, INMIC 2002, December 27-28, Karachi, Pakistan.

19.  S. A. Khan and N. A. Riza, “Demonstration of 3-Dimensional Wide Angle No-Moving Parts Laser Beam Steering,” SPIE 49th Annual Meeting, SPIE Proc. Vol. 5550, Paper No.9, 2 – 6 August 2004, Denver,  Colorado.

20.  N. A. Riza, “Enabling the Ultimate in Optical Wireless Communications: The Zero Propagation Loss Design,” IEEE Communications Society 3rd International Symposium on High Capacity Optical Networks and Enabling Technologies (HORNET) 2006 Conference, Charlotte, NC, Sept. 6-8, 2006.

21.  P. J. Marraccini and N. A. Riza, “Reconfigurable Visible Wireless Optical Link for Indoor Applications,” Royal Irish Academy (RIA) Communications and Radio Science Conference, Dublin, March 30, 2012.

22.  N. A. Riza, “ Flexible Agile Hybrid Optical-RF Antenna System for Communications and Radar,” 19th IEEE International Conference on Microwaves, Radar & Wireless Communications, Warsaw, Poland, May 23, 2012.

23.  N. A. Riza and P. J. Marraccini, “Power Smart In-door Optical Wireless Link Applications,” 8th IEEE International Wireless Communications and Mobile Computing Conference (IWCMC), Limassol, Cypress, August 27-31, 2012.

24.  P. J. Marraccini and N. A. Riza, “Dual Mode Indoor Optical Wireless Data Link Design using Micro-Optics For Robust Energy Efficient Operations,” EOS Ann. Mtg. Proc., Aberdeen, 2012.

25.  N.A.Riza and P.J.Marraccini,“Programmable optic-based robust underwater/free-space optical data transfer link designs for applications using high power lasers,” Photonics Ireland Conference Proceedings, Sept. Cork, 2015.

26. N. A. Riza, “Digital MEMS CAOS Camceiver and a User Positioning and IR ID Data Monitoring System for Indoor Optical and RF Wireless Environments,” IEEE Optical MEMS Conf. Proc, July 30, 2018.

27. N. A. Riza, “The Camceiver: Empowering Robust Agile Indoor Optical Wireless for Massive Data Centres,” in 42nd IEEE International Conference on Telecommunications and Signal Processing (TSP), pp. 445-448, July 2019.

28. N. A. Riza, “Smart Optical Beamforming for Next Generation Wireless Empowered Communications, Power Transfer, Sensing and Displays: Building on the Past,” IEEE ISSC Conference Proc. paper, June 9-10, Cork, Ireland, 2022.

— Fiber-Optic Switching, Wavelength Routing, Attenuation, and Filtering including Tunable Laser Designs

Journal Publications:

1.     N. A. Riza, D. L. Polla, W. P. Robbins, and D. E. Glumac, “High Resolution 50 nm Linear Displacement Macroscale Meander-line PZT Actuator,” IEE Electronic Letters (U.K.), Vol.29, No.18, Sept. 02, 1993.

2.     N. A. Riza, “High optical isolation low loss moderate switching speed nematic liquid crystal optical switch,” Optics Letters, Vol. 19, No.8, pp.1780-1782, 1994.

3.     N. A. Riza and S. E. Saddow, “Optically Controlled Photoconductive N-bit Switched Microwave Signal Attenuator”, IEEE Microwave & Guided Wave Lett., Vol.5, No.12, pp.448-450 Dec. 1995.

4.     N. A. Riza and J. Chen, “ Ultra-High –47 dB Optical Drop Rejection Multi-Wavelength Add-Drop Filter using Spatial Filtering and Dual Bulk Acousto-Optic Tunable Filters, “Optics Letters, Vol.23, No.12, pp.945-947, June 15, 1998.

5.     N. A. Riza and S. Yuan, “ Demonstration of a liquid crystal adaptive alignment tweeker for high speed infrared band fiber-fed free-space systems,” Optical Engineering, Vol.37, No.6,  June, 1998.

6.     N. A. Riza and S. Sumriddetchkajorn, “ Fault Tolerant Dense Multi-Wavelength Add/Drop Filter using a Two Dimensional Digital Micromirror Device, “ OSA Applied Optics-LP, Vol. 37, Issue 27, Page 6355 (September 1998).

7.     N. A. Riza and S. Yuan, “ Low Optical Interchannel Crosstalk, Fast Switching Speed, Polarization Independent 2×2 Fiber Optic Switch using Ferroelectric Liquid Crystals,” Electronics Letters, Vol.34, No.13,  25th June, 1998.

8.     N. A. Riza, “High Speed Multiwavelength Photonic Switch,”  Research Article Selected for the OSA Optics & Photonics News (OPN) Magazine, Optics in 1998 Special Issue, Dec., 1998.

9.     N. A. Riza and N. Madamopoulos, “ Synchronous amplitude and time control for an optimum dynamic range variable photonic delay line,” Applied Optics , Vol.38, No.11, pp.2309-2318, 10 April  1999.

10.  N. A. Riza and S. Sumriddetchkajorn, “ Digitally controlled fault tolerant multiwavelength programmable fiber-optic attenuator using a two dimensional digital micromirror devices,” OSA Optics Letters, Vol. 24, Issue 5, Page 282, March 1, 1999.

11.  S. Yuan and N. A. Riza, “General formula for coupling loss characterization of single mode fiber collimators using gradient-index rod lenses,” OSA Applied Optics, Vol.38, No.15, pp.3214-3222, May 20,  1999. Erratum, Applied Optics, Vol.38, No.30, p.6292, Oct.1999.

12.  N. A. Riza and S. Sumriddetchkajorn, “Small Tilt Micromirror Device-based Multiwavelength Three Dimensional 2 ´ 2 Fiber-Optic Switch Structures,” Optical Engineering, Vol.39, No.2, pp.379-386, Feb. 2000.

13.  N. A. Riza and S. Sumriddetchkajorn, “Versatile Multi-Wavelength Fiber-Optic Switch and Attenuator Structures using Mirror Manipulations,” Optics Communications, 169 (233-244), Oct.1, 1999.

14.  N. A. Riza and S. Yuan, “ Reconfigurable wavelength add-drop filtering based on a Banyan network topology and ferroelectric liquid crystal fiber-optic switches,” IEEE/OSA Journal of Lightwave Tech., Vol.17, No.9, Sept. 1999.

15.  N. A. Riza, “Fault-tolerant high speed variable fiber-optic attenuator using micromirrors,”  Research Article Selected for the OSA Optics & Photonics News (OPN) Magazine, Optics in 1999 Special Issue, Dec., 1999.

16.  N. A. Riza and S. Sumriddetchkajorn, “Micromechanics-based wavelength-sensitive photonic beam control architectures and applications,” Applied Optics, Vol. 39, No. 6, pp. 919-932,20 Feb. 2000.

17.  S. Sumriddetchkajorn and N. A. Riza, “Fiber-connectorized multiwavelength 2×2 switch structure using a fiber loop mirror,” Optics Communications, Vol. 175, pp. 89-95, 15 Feb. 2000.

18.  N. Madamopoulos and N. A. Riza, “All-fiber connectorized compact fiber optic delay-line modules using three-dimensional polarization optics,” SPIE Optical Engineering, Vol. 39, No. 9, pp. 2338-2344, September 2000.

19.  N. A. Riza and S. Sumriddetchkajorn, “Fault-tolerant variable fiber-optic attenuator using three dimensional beam spoiling,” Optics Communications, Vo.185, 103-108, Nov.1, 2000.

20.  N. A. Riza and Z. Yaqoob, “Sub-microsecond speed variable optical attenuator using acousto-optics,” IEEE Photonics Technology Letters, Vol. 13, No. 7, pp. 693-695, July 2001

21.  S. Sumriddetchkajorn, N. A. Riza and D. K. Sengupta, “Liquid crystal-based self-aligning 2×2 wavelength routing module,” Optical Engineering, Vol. 40, Issue 8, August 2001, pp.1521-1528

22.  M. J. Mughal and N. A. Riza, “Compact acousto-optic high speed variable attenuator for high power applications,” IEEE Photonics Technology Letters, 14(4), 510-512, April (2002)

23.  S. Sumriddetchkajorn and N. A. Riza, “Fault-tolerant three-port fiber-optic attenuator using small tilt micromirror device,” Optics Communications, April 2002, pp. 77-86.

24.  N. A.  Riza and M.J. Mughal, ‘Variable Attenuator for Fast-Response, High-Optical-Power Applications,’ OSA Optics and Photonics (OPN) News, pp. 41, December 2002.

25.  M. van Buren and N. A. Riza, “ Foundations for low loss fiber gradient-index lens pair coupling with the self-imaging mechanism,” OSA Applied Optics, LP, Vo.42, No.3, Jan. 20, 2003.

26.  N. A. Riza and M. J. Mughal, “Broadband optical equalizer using fault tolerant digital micromirrors,” Optics Express Internet Journal,  Vol. 11, pp.1559-1565, June 30, 2003.  http://www.opticsexpress.org/abstract.cfm?URI=OPEX-11-13-1559

27.  N. A. Riza, M. A. Arain, and S. A. Khan, “Analog-Digital Variable Fiber-Optic Delay Line,” IEEE/OSA Journal of Lightwave Technology, vol.22, No.2, pp.619-624, Feb. 2004.

28.  N. A. Riza and S. A. Khan, ” Liquid Crystal Deflector-based Variable Fiber-Optic Attenuator “, Applied Optics, Vol. 43, No.17, 3449-3455, June 2004.

29.  M. J. Mughal and N. A. Riza, “Variable fiber-optic attenuator using bulk micromachined deformable micromirror,” Optical Engineering, Vol.43, Oct.10 2004. (also on-line published in OE letters June 17, 2004.

30.  N. A. Riza and F. N. Ghauri, “Hybrid Analog Digital MEMS Fiber Optic Variable Attenuator,” IEEE Photonic Technology Letters, Vol.17, No.1, pp. 124-126, Jan. 2005

31.  N. A. Riza and N. Madamopoulos, “ Compact switched retroreflection-based 2×2 optical switching fabric for WDM applications”, IEEE/OSA Journal of Lightwave Technology, Vol.23, No.1, pp.247-259, Jan. 2005.

32.  N. A. Riza and M. J. Mughal, “Fiber-Optic Tunable Multiwavelength  Variable Attenuator and Routing Modules, ” Applied Optics, Vol.44, No.5, pp..792-799, Feb., 2005.

33.  Z. Yaqoob and N. A. Riza, “Bulk acousto-optic wavelength agile filter module for wavelength-multiplexed optical scanner,” Applied Optics, Vol.44, No.13, May 1, 2005.

34.  N. A. Riza and S. A. Khan, “ Wavelength tunable variable fiber optic attenuator using liquid crystal-mirror hybrid controls,” IEEE Photon. Tech. Lett., Vol.17, No.3, pp.621-623, March 2005.

35.  N. A. Riza and F. N. Ghauri, “ Super resolution variable fiber-optic attenuation instrument using digital micromirror device,” AIP Rev. Scientific Instru., Vol.76, No.1, 2005.

36.  W. Sun, W. Noell, M. Zickar, M. J. Mughal, F. Perez, N. A. Riza and N. F. De Rooij, “Design, Simulation, Fabrication, and Characterization of a Digital Variable Optical Attenuator,” IEEE J. of MEMS, 2006.

37.  S. A. Khan and N. A. Riza, “Demonstration of a MEMS Digital Micromirror Device-based broadband reconfigurable optical add-drop filter for dense wavelength division multiplexing systems,” IEEE/OSA Journal of Lightwave Technology, 2006.

Conference Publications:

1.    N. A. Riza, and D. L. Polla “Micromechanical fiber-optic switches for optical networks,” Integrated Optics and Microstructures OE/Fibers Conference  Proceedings of the SPIE, Vol. 1790,  Sept., 1992.

2.    N. A. Riza and S.E. Saddow, “N-bit optically controlled microwave signal attenuator using the photoconductive effect,” SPIE Proc., Vol. 2560, pp.9-18, 1995.

3.     J. Kim and N. A. Riza, “Fiber Array Optical Coupling Design Issues for Photonic Beamformers,” SPIE Proc, pp.271-282,  Orlando, April, 1996.

4.    N. A. Riza and Shifu Yuan, “Robust Packaging of Photonic RF Modules using Ultra-Thin Adaptive Optical Interconnect Devices,” SPIE Conf. on Optical Technology for Microwave Applications VIII, Vol.3160, pp.170-177, San Diego, August 1997.

5.    N. A. Riza, “ Low Interchannel crosstalk wavelength routing switch based on bulk acousto-optic tunable filters,” IEEE LEOS Ann. Mtgs. Digest, Vol.2, ThH2, pp.341-342, Nov., 1997.

6.    N. A. Riza and N. Madamopoulos, “ All-fiber connectorized fiber-optic delay module using 3-D polarization optics,” IEEE LEOS Ann. Mtgs. Digest, Vol.2, ThW2, pp.472-473, Nov., 1997.

7.    N. A. Riza and N. Madamopoulos, “Single micro-optical bench fiber connectorized delay module using bulk polarization optics,” The 8th Ann. DARPA Symp. on Photonic Systems for Antenna Applications, Post-deadline Paper, pp.1-5, Jan. 1998.

8.     N. A. Riza, “ Ferroelectric Liquid Crystal Polarization Switching-based High Speed Multi-Wavelength Add/Drop Filters using Fiber and Array Waveguide Gratings, “ International Optics in Computing ‘98 Conference, SPIE Vol.3490, P39, pp.335-338, Brugge, Belgium, June 1998.

9.    N. Madamopoulos and N. A. Riza, “ Reversible fiber-optic switched delay module using GRIN lens fiber-optic collimators and ferroelectric liquid crystals,” IEEE LEOS Ann. Mtgs. Digest, Dec., 1998.

10.    Shifu Yuan and N. A. Riza, “ Low interchannel crosstalk high speed fiber-optic N X N crossconnect switch using polarization optics and ferroelectric liquid crystals,” IEEE LEOS Ann. Mtgs. Digest, Dec., 1998.

11.    N. A. Riza and Sarun Sumriddetchkajorn, “Two Dimensional Digital Micromirror Device-based 2 x2 fiber-optic switch array, “IEEE LEOS Ann. Mtgs. Digest, Dec., 1998.

12.    S. Sumriddetchkajorn and N. A. Riza, “Fault-tolerant multiwavelength fiber-optic beam control systems using microelectromechanical systems,” OSA Annual Meeting, TuSS2, Santa Clara, CA, Sept. 1999.

13.    N. A. Riza and S. Sumriddetchkajorn, “Multiwavelength Three Dimensional 2 ´ 2 Fiber-Optic Switch Structure using Small Tilt Micro-Mirrors,” ICO XVIII: Optics in the Next Millenium, SPIE Vol. 3749, pp. 470-471, San Francisco, CA, Aug. 1999.

14.  Sarun Sumriddetchkajorn and N. A. Riza, “ Fault-Tolerant Multichannel Programmable Polarization Dependent Loss and Gain Compensator Structures using Small Tilt Micromirrors,” National Fiber Optic Engineers Conference, Chicago, Sept., 1999.

15.  S. Sumriddetchkajorn and N. A. Riza, “Multi-Wavelength 2´2 Fiber-Optic Switch Structure using Mirror Array,” IEEE-LEOS Annual Meeting, San Francisco, CA, Nov. 1999.

16.  S. Sumriddetchkajorn, D. K. Sengupta, and N. A. Riza, “Self-Aligning 2×2 Fiber-Optic Switch using Liquid Crystals,” IEEE-LEOS Annual Meeting, San Francisco, CA, Nov. 1999.

19. S. Sumriddetchkajorn and N. A. Riza, “Micromachine-based fault-tolerant high resolution high-speed programmable fiber-optic attenuator,” Optical Fiber Communication Conference, pp. ThQ1-1-ThQ1-3, Baltimore, Maryland, March 2000.

18. S. Sumriddetchkajorn and N. A. Riza, “All-fiber add/drop wavelength routing structure,” Proceedings of SPIE, Vol. 4046, paper 12, Orlando, Florida, April 26, 2000.

19. N. A. Riza and Y. Huang, “Digital fault-tolerant variable fiber-optic attenuator using liquid crystals,” Proceedings of SPIE, Vol. 4046, paper 11, Orlando, Florida, April 26, 2000.

20. R. A. W. Gelissen, Y. Huang and N. A. Riza, “Polarization control using nematic liquid crystals,” Proceedings of SPIE, Vol. 4046, paper 13, Orlando, Florida, April 26, 2000.

21. N. A. Riza and Z. Yaqoob, “High-speed programmable optical attenuator,” Proceedings of SPIE, Vol. 4046, paper 10, Orlando, Florida, April 26, 2000.

22. N. A. Riza, “ Liquid crystal electro-optical switching approaches,” OSA Integrated Photonics Research (IPR) Topical Meeting, IthE2-1, pp.99-101, 12-15 July 2000, Quebec, Canada.

23. N. A. Riza , R. Akbar, S. Sumriddetchkajorn, F. Perez, and M. J. Mughal, “ 47 dB dynamic range sub-microsecond switching speed variable fiber-optic attenuator for fast transient fiber-optics,” OSA Topical Meeting on Photonics Switching, Postdeadline Paper PDP2, June 15, Monterey, CA, 2001.

24. N. A. Riza and Z. Yaqoob, “ Intelligent multi-fiber interface module for high bit rate inter-processor data transfer,” Paper We.A.1.4, Symp. On Optical Interconnects, 27th European Conference on Optical Communication, ECOC 2001, Oct. 2, Amsterdam, Netherlands.

25.  M. J. Mughal and N. A. Riza, “65 dB dynamic range 2.8 microseconds switching speed variable fiber-optic attenuator,” 27th European Conference on Optical Communication, Post deadline paper, ECOC 2001, Vol. 6, pp. 56-57, Sep-Oct, 2001.

26.  N. A. Riza and M. J. Mughal, “Fault-tolerant photonics for routing and gain controls,” WDM and Photonic Switching Devices for Network Applications III, Optoelectronics 2002, Photonics West, SPIE Proc. Vol. 4653, paper 04, 19-25 January 2002, San Jose, California, USA

27.  W. Sun, M. J. Mughal, W. Noell, F. Perez, N. A. Riza, and N. de Rooij, ‘Design and Simulation of a 16-bit Variable Optical Attenuator,’ Proceedings 2002 IEEE/LEOS International Conference on Optical MEMS, Lugano, Switzerland,  pp. 53-54. 2002.

28.  W. Sun, J. Mughal, F. Perez, W. Noell, N. Riza and Nico De Rooij, ‘A Bulk Micromachined Tiltable Mirror Array Digital Variable Optical Attenuator,’ Transducers 03., Paper 4D.1.3, 12th IEEE International Conf. on Solid State Sensors, Actuators, and MicroSystems,  Boston. June 8-12, 2003.

29.  W. Sun, J. Mughal, F. Perez, W. Noell, N. Riza and Nico de Rooij, “A Bulk Micromachined Tiltable Mirror Array Digital Variable Optical Attenuator,” CLEO/QELS 2003. Baltimore, Maryland. 2003.

30.  N. A. Riza and M. J. Mughal, “An Approach towards the Holy Grail in All-Optical Circuit Switching: The Monster All-Optical Crossconnect,” SPIE Photonics North Conference, Paper 101-486, May 26-29, Montreal, Canada, 2003.

31.  W. Sun, J. Mughal, F. Perez, W. Noell, N. Riza and Nico De Rooij, ‘A Bulk Micromachined Tiltable Mirror Array Digital Variable Optical Attenuator,’ Optical MEMS 03., IEEE LEOS International Conf. on Optical MEMS,  Hawaii. August, 2003.

32.  M. J. Mughal and N. A. Riza, “Deformable micromirror-based variable fiber-optic attenuator,” NFOEC 2003 Technical Proc., pp.137-140, Orlando, FL, Sept. 2003.

33.  N. A. Riza and M. J. Mughal, “Fiber-optic multi-wavelength variable attenuator using bulk acousto-optics,” International Conference on Photonics Switching: PS 2003, Versailles, France, Sept.26-Oct.2, 2003.

34.  W. Sun, M.J. Mughal, W. Noell, F. Perez, N.A. Riza, N.F. de Rooij, “Fabrication and Measurement of a Circular Digital Variable Optical Attnuator”, The IEEE/LEOS Optical MEMS 2004, pp. 35-36,Takamatsu, Japan, 2004.

35.  S. A. Khan and N. A. Riza, “High Resolution Broadband Variable Fiber-Optic Attenuator using Liquid Crystals,” Optics in the Southeast (OISE), Organized by School of Optics/CREOL University of Central Florida, SPIE and Optical Society of America, Orlando, FL, Nov. 12-13, 2003.

36.  W. Sun, M. J. Mughal, F. Perez, N. A. Riza, W. Noell, and Nico De Rooij, ‘Design and fabrication of a circular Digital Variable Optical Attenuator,’ Photonics Europe Conf. on MEMS, MOEMS, and Micromachining, SPIE Vol.5455, No.28, April 29-30, Strasbourg, France, 2004.

37.  Nabeel A. Riza and Muzammil A. Arain, “Code Multiplexed Holography based All-Optical N×N Switch” , Photonics in the South East, Sponsored by University of central Florida, OSA, and SPIE, SE-03-D3, Orlando, Florida, November 12-13, (2003).

38.  N. A. Riza and F. N. Ghauri,, “Hybrid Design MEMS Variable Optical Attenuator for Simultaneous High Dynamic Range and High Resolution Controls,” European Conference on Optical Communication, ECOC 2004, Stockholm, Sweden,  Sept. 5-9, 2004.

39.  S. A. Khan and N. A. Riza, “Wavelength tunable and broadband variable fiber-optic attenuators using liquid crystals,” Proceedings of SPIE, Vol. 5814, Paper No. 5814-4, Enabling Photonics Technologies for Defense, Security, and Aerospace Applications, in Defense and Security Symposium 2005, Orlando, Florida, USA , March 28-April 01, 2005.

40.  F. N. Ghauri and N. A. Riza, “Super High Performance MEMS VOAs for Aerospace and Commercial Application,” Proceedings of SPIE, Vol. 5814, Paper No. 5814-22, Enabling Photonics Technologies for Defense, Security, and Aerospace Applications, in Defense and Security Symposium 2005, Orlando, Florida, USA ,  March 28-April 01, 2005.

41.  N. A. Riza, “Liquid Crystal Agile Photonics – From Fiber to the Free-Space Domain,” Conf. on Liquid Crystals Optics and Applications LCOA/COO-2005, Editor, Tomasz Wolinski,  SPIE International Congress on Optics and OptoElectronics, Warsaw, Poland, Aug. 2005.

Patents – Communications and Switching & Controls

N. A. Riza and D. L. Polla, “Micro-dynamical fiber-optic switch,” U.S.A. Patent No.5,208,880, May 4,   1993.
M. C. DeJule, T. L. Credelle, N. A. Riza, and D. E. Castlebery, “Compact polarization independent optical switching units,” U.S.A. Patent No. 5,319,477, June 7, 1994.
M. C. DeJule, T. L. Credelle, N. A. Riza, and D. E. Castlebery, “ “Compact polarization dependent optical switching units,” U.S.A. Patent No. 5,345,321, Sept. 06, 1994.
M. C. DeJule, N. A. Riza, D. E. Castlebery, and T. L. Credelle, “Optical interferometric device with spatial light modulators for switching substantially coherent light,” U.S.A. Patent No. 5,373,393, Dec. 13, 1994.
N. A. Riza, J. E. Hershey, and A.  A. Hassan, “Optical communication system using coplanar light modulators,” U.S.A. Patent No. 5,410,147, April 25, 1995.
N. A. Riza, D. E. Castleberry, T. L. Credelle, and M. C. DeJule “Interferometric spatial switch for polarized or unpolarized light using liquid crystal,” U.S.A. Patent No.5,477,350, Dec. 19, 1995.
N. A. Riza, “Fast switching liquid crystal switching unit,” USA Patent No. 5,568,286, Oct.22, 1996.
J. E. Hershey,  N. A. Riza,  and A. A. Hassan, “Optical synchronization algorithm and apparatus,” USA Patent No. 5,532,860, July 2, 1996.

N. A. Riza, “Digitally Control Polarization-based Optical Scanner,” US Patent 6,031,658, Feb.29, 2000
N. A. Riza, “ Fault-tolerant fiber-optical beam control modules,” Patent No. 6,222,954, April 24, 2001.
N. A. Riza, “ High speed fiber-optic switch,” Patent No. 6,282,336, August 28, 2001.
N. A. Riza, “ Polarization-based fiber-optic switch,” Patent No. 6,360,037, March 19, 2002.
N. A. Riza, “ Multi-technology multi-beam-former platform for robust fiber-optical beam control modules,” Patent No. 6,525,863, Feb. 25, 2003.
N. A. Riza, “High resolution fault-tolerant fiber-optical beam control modules,” Patent No. 6,563,974, May 13, 2003.
N. A. Riza, “Multiplexed Optical Scanner Technology,” Patent No. 6,687,036, Feb.3, 2004.
N. A. Riza, “Fault-tolerant fiber-optical multiwavelength processor,” Patent No. 6,859,578 B2, Feb. 22, 2005.
N. A. Riza, “ High speed fiber-optic attenuation modules,” Patent No. 6,885,807, April 26, 2005.
N. A. Riza and M. J. Mughal, “ Electronically tunable optical filtering modules,” Patent No. 6,982,818, January 3, 2006.

N. A. Riza, “Multiple mode wireless data link design for robust energy efficient operation,” USA Patent Application Publication Number 20140161466, June 12, 2014.