| 1. |
- Agrell, Erik, 1965, et al.
(författare)
-
Power-efficient modulation formats in coherent transmission systems
- 2009
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 27:22, s. 5115-5126
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent optical transmission systems have a four-dimensional (4-D) signal space (two quadratures in two polarizations). These four dimensions can be used to create modulation formats that have a better power efficiency (higher sensitivity) than the conventional binary phase shift keying/quadrature phase shift keying (BPSK/QPSK) signals. Several examples are given, with some emphasis on a 24-level format and an 8-level format, including descriptions of how they can be realized and expressions for their symbol and bit error probabilities. These formats are, respectively, an extension and a subset of the commonly used 16-level dual-polarization QPSK format. Sphere packing simulations in 2, 3, and 4 dimensions, up to 32 levels, are used to verify their optimality. The numerical results, as the number of levels increases, are shown to agree with lattice-theoretical results. Finally, we point out that the use of these constellations will lead to improved fundamental sensitivity limits for optical communication systems, and they may also be relevant as a way of reducing power demands and/or nonlinear influence. © 2009, IEEE. All rights reserved.
|
|
| 2. |
|
|
| 3. |
- Campi, Roberta, et al.
(författare)
-
Highly reliable and high-yield 1300-nm InGaAlAs directly modulated ridge fabry-Perot lasers, operating at 10-gb/s, up to 110°C, with constant current swing
- 2006
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 24:1, s. 143-149
-
Tidskriftsartikel (refereegranskat)abstract
- Transceivers for 300-m multimode links, based on a serial 10-Gb/s laser source and incorporating a receiver based on electronic dispersion compensation (EDC), are creating the first high-volume application for a 10-Gb Fabry-Perot (FP). A highly reliable and high-yield uncooled ridge FP laser is presented. The device shows excellent power characteristics in the 25 divided by 150 degrees C temperature range with very high To (95 K in the temperature range 0 divided by 85 C and still 78 K at 150 degrees C). Outstanding dynamic performances are also shown: 6 dB of extinction ratio can be achieved up to 110 degrees C by using a constant current swing of 50 mA. Because of their enhanced performances, these devices have enabled single temperature setting of the optical module, leading to a significant test cost reduction.
|
|
| 4. |
- Chacinski, Marek, et al.
(författare)
-
Monolithically Integrated 100 GHz DFB-TWEAM
- 2009
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 7:16, s. 3410-3415
-
Tidskriftsartikel (refereegranskat)abstract
- A monolithically integrated distributed feedback (DFB) laser and traveling-wave electro-absorption modulator (TWEAM) with >= 100 GHz -dBe bandwidth suitable for Non-return-to-zero (NRZ) operation with on-off keying (OOK) is presented. The steady-state, small-signal modulation response, microwave reflection, chirp characteristic, and both data operation and transmission were investigated. The DFB-TWEAM was found to be an attractive candidate for future short distance communication in high bitrates systems.
|
|
| 5. |
- Chen, D. R., et al.
(författare)
-
High-Resolution Strain/Temperature Sensing System Based on a High-Finesse Fiber Cavity and Time-Domain Wavelength Demodulation
- 2009
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 27:13, s. 2477-2481
-
Tidskriftsartikel (refereegranskat)abstract
- A high-resolution strain/temperature sensing system based on a fiber Bragg grating-Fabry-Perot cavity (FBG-FPC) and a wavelength-swept single-longitudinal-mode laser diode (modulated by a sawtooth signal) is proposed. The high-finesse (similar to 627) FBG-FPC formed by two uniform FBGs of high reflectivity (similar to 99.5%) is used both as a strain/temperature sensor and a FPC with ultranarrow (similar to 0.12 pm) transmission bands. Using a photodetector to detect the transmissive light of the laser diode through the FBG-FPC, wavelength demodulation is achieved by mapping wavelength measurement to time measurement. Both strain sensing and temperature sensing with a resolution of 0.11 mu epsilon and 0.014 degrees C, respectively, have been demonstrated.
|
|
| 6. |
- Dai, Daoxin, et al.
(författare)
-
Compact Microring Resonator With 2 x 2 Tapered Multimode Interference Couplers
- 2009
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 27:21, s. 4878-4883
-
Tidskriftsartikel (refereegranskat)abstract
- Compact microring resonator devices are realized by using a small SU-8 polymer strip waveguide that has an SU-8 polymer core (n similar to 1.573), an SiO2 buffer (n similar to 1.445), and an air cladding. Due to the high index contrast of the optical waveguide, a small bending radius (similar to 150 mu m) is used for the MRR. To enhance the coupling between the access optical waveguides and the microring, 2 x 2 multimode interference couplers are used. The measured spectral response of the through port shows a high extinction ratio of over 15 dB and a 3-dB bandwidth of about 0.38 nm (corresponding to a moderate Q-value of similar to 4500).
|
|
| 7. |
- Dai, Daoxin, et al.
(författare)
-
Deeply etched SiO2 ridge waveguide for sharp bends
- 2006
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 24:12, s. 5019-5024
-
Tidskriftsartikel (refereegranskat)abstract
- A deeply etched SiO2 ridge waveguide including the buffer, core, and cladding is presented for realizing sharp bends. The present SiO2 ridge waveguide has a strong confinement at the lateral direction, while it has a weak confinement at the vertical direction. Due to the strong confinement, a sharp bend (with a very small bending radius of about 10 mu m) is obtained for an acceptable bending loss. A detailed analysis of the loss in a bent waveguide is given by using a finite-difference method. In order to reduce the transition loss, a narrow bending section with an optimal lateral offset is used. A low leakage loss is obtained by using wide straight waveguides, and linear tapers are used to connect the wide straight section and narrow bent sections.
|
|
| 8. |
|
|
| 9. |
- Dai, D. X., et al.
(författare)
-
Ultrasmall thermally tunable microring resonator with a submicrometer heater on Si nanowires
- 2008
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 26:5-8, s. 704-709
-
Tidskriftsartikel (refereegranskat)abstract
- An ultracompact widely tunable thermooptical (TO) microring resonator (MRR) filter based on Si nanowires is presented. The Si nanowire waveguide has a SiO2 insulator, Si core, a SiO2 up-cladding, and a thin metal film at the top. The metal circuit along the microring is used as a submicrometer heater which has the same width as the Si nanowire waveguide. The up-cladding is optimized to reduce the light absorption of the metal as well as to have a good heat-conduction from the heater to the Si core. Two pads used as the contact points for the probes connecting to the electrical power are perpendicularly connected to the microring by using optimized T-junctions (with a low excess loss of about 0.06 dB per T-junction). With such a design, the present thermally tunable microring resonator (MRR) can be fabricated by using a standard fabrication process with a single lithography process, which is much simpler than the fabrication with double lithography processes used for the conventional TO components. Finally, the simulation results show that the designed MRR has a wide tuning range of about 20 nm with a low heating power of 5 mW.
|
|
| 10. |
- de Rossi, S., et al.
(författare)
-
Longitudinal mode selection in constricted photonic crystal guides and electrically injected lasers
- 2005
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 23:3, s. 1363-1368
-
Tidskriftsartikel (refereegranskat)abstract
- Locally reducing the width of a wide photonic crystal (PhC) waveguide generates a constriction which acts as an internal reflector. We have simulated and measured the spectral behavior of a wide PhC waveguide locally constricted to a narrower PhC waveguide and ended by two cleaved facets, thus generating two coupled cavities. Passive structures as well as electrically injected active structures have been investigated. The multimode behavior of wide PhC waveguides is evidenced to play a deciding role. Modal reflection and transmission at the constriction are simulated and measured on passive PhC waveguides, when varying the constrictions' hole size and length. The spectral behavior of full-PhC electrically pumped lasers including such a constriction is measured and analyzed according to the constriction geometry. Design rules are finally proposed to take advantage of this coupled-cavities behavior for high rejection and high external efficiency monomode laser operation.
|
|
