In the paper, we have proposed a structure with only one photonic crystal (PC) micro-cavity side-coupled to a PC
one-way waveguide to generate strong on-resonance optical delay. According to the coupled mode theory (CMT),
the resonator system can maintain a 100% transmission spectrum throughout the complete resonant bandwidth,
which is also demonstrated by the numerical results calculated by the finite element method (FEM). As a temporal
Gaussian pulse is launched, the simulation results show that the device introduces a strong pulse delay while
maintaining total transmission efficiency within the resonant bandwidth, and the resonator structure may be of great
significance for making delay lines in optical buffer applications.
We design a highly efficient channel drop filter (CDF) with only one channel drop micro-cavity based on photonic
crystal (PC) one-way waveguide. By means of the new nature of waveguide-cavity interaction, over 95% channel drop
efficiency can be realized in the structure. Some multichannel drop filters with high drop efficiencies are also engineered
based on such the structure. These numerical results are all calculated by using the finite element method (FEM), which
agrees well with the theoretical analysis result.
A reconfigurable optical add/drop multiplexer (R-OADM) device is proposed based on 2-D photonic crystals (2-D PCs) with a triangular lattice of air holes. It consists of channel add/drop filters, two bends with 120-deg bending angles, and a 2×2 directional coupler switch. Chirp structures are introduced in the directional coupler switch to improve its extinction ratio. At =1550 nm, the device is ultracompact with a net footprint 30×22 µm, excluding its external device. It is far smaller in size than other corresponding devices implemented through ring resonators. The device is numerically calculated by the finite-difference time-domain (FDTD) method, and simulation results confirm that the R-OADM device can be used for dynamically wavelength routing.
We present a complete analysis on improving the gain flatness of ultrabroadband tellurite fiber Raman amplifiers (TFRAs) by optimizing the parameters of multiwavelength pumps. Compared to conventional TFRAs, our amplifier has low gain ripple despite the ultrawide amplification bandwidth: well below 3.78% (5.66%, 11.98%) with respect to the average net gain 10 dB over a 120-nm (140-, 160-nm) bandwidth. In addition, we investigate the fractional gain contribution from each pump wavelength for the optimal 140-nm TFRA, and observe that the configuration is effective in equalizing the peculiar dual-peak gain spectra produced by multiple pumps. Finally, we calculate the noise figure for the 140-nm TFRA with a vibration less than 3 dB.
A kind of optical coarse packet switching based on optical label routing is intrduced. In the switching, the swapping granularity is coarse compared to common optical packet switching, and the header of optical packet is labeled by multi-wavelengths. Some realization techniques on core switching node and edge node with terminator are studied. A principle experiment system is established to perform the optical coarse packet transmitting, switching, and receiving, and verify the feasibility of such optical coarse packet switching.
In this paper, dispersion compensating photonic crystal fiber with triple-cladding is put forward and the property of high negative dispersion is investigated. Plane-wave expansion (PWE) method is used to analyze. We discuss the variation of the dispersion in detail, with changing the geometry parameters. A triple-cladding dispersion compensating photonic crystal fiber with dispersion -4140 ps/nm/km and FWHM 10 nm is demonstrated at 1550 nm wavelength.
A kind of optical multi-wavelength label switching adopting Gigabit Ethernet technology is introduced. In this switching, optical header is labeled by several optical pulses at different wavelengths in the same optical communication channel band as optical payload, and a specific Gigabit Ethernet adapter is used as the optical payload sender and receiver. The principle of optical switching is explained, and a demonstration experiment is described.
Both protection and restoration are fundamental consideration in designing robust optical networks, especially in challenging GMPLS/ASON architecture. Fast Rerouting technology as one important method of MPLS-Traffic Engineering is an efficient and powerful technology for protecting MPLS-TE LSPs from link and node failures. By supporting locally reparation of the affected LSPs at the point of failure, link and node protection are achieved quickly. The goal of real-time IP applications over native IP unicast/multicast networks or LDP based MPLS networks is to limit the IP packet loss duration in the network to 10s of milliseconds in the event of link/node failures. RSVP signaled LSP is used with explicitly routed path as the re-direct tunnel, while the protected traffic can be either MPLS traffic engineered LSPs, LDP based LSPs, IP unicast, IP multicast traffic or the mix of them. This mechanism can be applied to both point-to-point links and multi-access links in the cases of the link protection and node protection. Besides the above resilience research on IP/MPLS single layer, tests or experiments on multilayer mechanism, i.e. optical and IP/MPLS network layer composing of multi-vendor routers and multi-domain, are carried out by a number of famous organizations and companies where optical dedicated/shared mesh protection/restoration and MPLS fast rerouting survivable techniques are combined to guard against both dual link failures and combined link and IP/MPLS hardware and software router failures. Those techniques used in next-generation backbone network design result in that not only familiar failures such as fiber cuts or amplifier damage but also system failures such as router failures or multiple concurrent failures can be recovered fast and effectively at corresponding layer. In this paper, on the basis of analysis of IETF's internet drafts about fast rerouting algorithm and standards in MPLS-TE and GMPLS, new fast rerouting algorithm and corresponding simulation results are proposed step by step. At the same time, resilient performance in a GMPLS/ASON design especially under mesh optical protection is studied carefully while a few coming function requirements in OXC and router equipments obtained from the above analysis are discussed to some extent. Figures and tables are presented for explaining the enhanced fast rerouting technology reducing confusion of packets and achieving falling delay time of rerouting. Finally, some issues for further work are to identify the importance where to place appropriate resilient mechanism in the next network design.
A new dual-pump fiber optical parametric amplifier (FOPA) is investigated, which is composed of three-section photonic crystal fibers (PCF) and theoretically provides a nearly flat gain of 21.54 dB with peak-to-peak gain uniformity of better than 0.2-dB over the 405-nm bandwidth from 1260 nm to 1665 nm. Moreover, the influence of random fluctuations of the second-order dispersion in each fiber segment on the gain spectrum also is analyzed. When the average values of second-order dispersions are maintained close to the constant optimum values, the deviation of gain spectra is not large and the gain ripple is not more than 3 dB in presence of second-order dispersion variations.
In order to reduce the complexity of the optical switching nodes at a reasonable level and increase its capacity at the same time, the concept of multi-granularity was proposed. With the utilization of multi-granularity switching, the number of ports for the optical switching matrices can be decreased. In this paper, we consider the two-stage multiplexing that includes the wavelength multiplexing and waveband multiplexing. A simple algorithm that can realize the grouping from wavelengths into wavebands efficiently is proposed. As the decreased number of the optical switching matrices' ports is determined partially by the number of the nodes passing the waveband path, the length of the waveband path is considered in this algorithm. To group as more wavelengths as possible into wavebands, all the wavelength paths will be evaluated in the algorithm as long as they have common sub-path. This algorithm is also tested in two networks with six nodes, and the saving number of the switching matrices' ports is compared with which using only the one-stage wavelength multiplexing.
A kind of multi-wavelength labeled optical packet switching technology is presented, in which optical header is consisted of several optical pulses in different wavelength that are in the same WDM optical channel band as optical signal payload. A probable scheme to realize such optical switching as well as an optical switching node structure is proposed. A simplify principle experiment has proved the possibility of such switching method.
The development of advanced optical networking technology put forward a requirement for a new control plane to implement such functionalities as resource discovery, state information dissemination, path selection, and path management. In this paper, the development and evolution of optical networks are analyzed at first, then the requirements for the unified control plane are put forward, finally, the functional modules and interface properties for the unified control plane are investigated in detail.
The basic technology of adaptive optical amplifier is introduced in this paper. How the performance of optical amplifier may meet the needs of application system is discussed according to the amplitude and shape of the input optical signal, the amplifier automatically adjusting the operating parameters. Taking the EDFA as an example, the feasibility to be realized technology of adaptive amplifier is investigated.
The properties of high rare-earth-containing borosilicate glasses have been investigated to assess the potential for using these materials to construct electromagnetic calorimeters for particle physics. We report here on measurements of scintillation yield, transmission and decay time, on large blocks of Ce3+-doped Gd2O3-based glasses. The samples were excited by a high energy X-ray beam and the associated scintillation yield and decay time was measured. The optical transmission of the samples was measured. It was observed that scintillation yield of present scintillation glass is 20% of BGO scintillation yield, decay time is in range of 50 - 80 ns, glass density is 5.50 g/cm3. It was concluded that higher light yield and density make this glass become promising candidate for cerium doped dense glass scintillator.
The properties of high rare-earth-containing germanate glass have been investigated to assess the potential for using this material to construct electromagnetic calorimeters for particle physics. We report here on measurements of scintillation yield, transmission and decay time, on large blocks of Ce3+-doped Gd2O3-based glasses, the samples were excited by a high energy X-ray beam and the associated scintillation yield and decay time was measured. The optical transmission of the samples was measured. It was observed that scintillation yield of present scintillation glass is 20 - 30% of BGO scintillation yield, decay time is in range of 60 - 90 ns, glass density is 5.75 g/cm3. It was concluded that higher density and availability and low cost make this glass become promising candidate for cerium doped dense scintillator.
Oxide glasses containing Ce were prepared by the conventional melting method under reducing atmosphere. Spectroscopic properties of the glasses were studied by steady-state luminescence spectroscopy. In the present paper we made a report to summarize the characteristics of excitation and emission spectra in difference oxide hosts.
The concentration effect of the spectroscopic properties of Yb3+-doped phosphate glasses have been determined from absorption and emission measurements at room temperature. The systematic variations of the spectroscopic properties and laser performance parameters with activator concentration can be used to optimize the doping concentration.
The properties of high rare-earth-containing borosilicate glass have been investigated to assess the potential for using this material to construct electromagnetic calorimeters for particle physics. We report here on measurements of scintillation yield, transmission and decay time, on large blocks of Ce3+-doped Gd2O3-based glasses, the samples were excited by a high energy X-ray beam and the associated scintillation yield and decay time were measured. The optical transmission of the samples was measured. It was observed that scintillation yield of present scintillation glass is 10 - 20% of BGO scintillation yield, decay time is in range of 60 - 80 ns, glass density is 5.40 g/cm(superscript 3$. It was concluded that higher density and availability and low cost makes this glass become promising candidate for cerium doped dense scintillator.
The concentration effect of the spectroscopic properties Yb3+-doped borate glasses have been determined from absorption and emission measurements at room temperature. The systematic variations of the spectroscopic properties and laser performance parameters with activator concentration can be used to optimize the doping concentration.
The stark energy level split of (2F7/2, 2F5/2) of ytterbium ion in glasses are derived from room temperature absorption and emission spectra. It is shown that the stark energy split increases as the base varies from phosphate to tellurite glasses, and the first and second stark energy levels lay in range of 150 - 250 cm-1, 350 - 450 cm-1 over ground, the first over ground has smaller energy and thus larger Boltzmann heat effect and is difficult in lasing at this terminal level. The second level is 350 cm-1 over ground and can be considered as the terminal level whose lasing wavelength varies from 1000 nm to 1020 nm. The partition function ratio of the upper and lower levels of ytterbium ion is calculated and more accurate reciprocity equation by which emission cross section is determined from absorption spectra is obtained from stark energy levels.
Advances in optical fiber amplifier for optical network are reviewed in this paper. Considerable progress has been made in optical amplifier technology in recent years. The bandwidth of amplifiers has increased several times and flat gain amplifiers with more than 80 nm of bandwidth have been demonstrated. With the advent of Raman fiber amplifiers, more wider bandwidth is obtained. Progress has also been made in the understanding of amplifier gain dynamics. Several control schemes have been successfully demonstrated to mitigate the signal impairments due to fast power transients in a chain of amplifiers and will be implemented in optical network design. Terrestrial optical systems have ben increasing in transmission capacity. In this review, we focus on the recent progress in some important aspects of several optical fiber amplifier technology.
In this paper the fluorescence quantum efficiencies and branch ratios of ytterbium doped oxide glasses are firstly calculated with equation derived from the reciprocity principle. It is shown that using absorption spectra of ytterbium doped glasses including borate, phosphate, niobosilicate, telluorogermanate and tellurite glasses, the fluorescence quantum efficiencies are obtained and varies from 80% to 99%, increasing with decreasing phonon energy of glass hosts. The branch ratios change slightly as glass hosts with different phonon energy and are about 40%, 30%, 30%, 0% around 970 nm, 1000 nm, 1020 nm, 1050 nm wavelength, respectively.
New dense oxide glass scintillator has been discovered in the system: B2O3-SiO2-Al2O3- Gd2O3 doped with trivalence cerium. This scintillator has a unique combination of properties including high scintillating light output, high density and desirable emission wavelength, large radiation hardness, short radiation length, and easy to produce in large size and low price. Here we compare the properties with those of the two recently developed dense scintillators: Ce3+-doped fluorophosphate glass and Ce3+-doped fluorohafnate glass, and with those of the three most widely used scintillating crystals Ce:YAP,CeF3 and BGO.
In this paper the glass formation, physical and spectroscopic properties of phospho-tellurate and germano- tellurate glasses are systematically studied. Yb3+- doped laser glasses with high stimulated emission cross- section are discussed.
The luminescence of Ce3+ in borate, borosilicate, phosphate and germanate glasses containing La2O3,BaO, Ta2O5,Nb2O5 were measured by ultraviolet-visible excitation with an aim of identifying the effect of hosts on the spectroscopic properties of Ce3+ in these glasses. Meanwhile, the scintillating luminescence of some of these borate glasses were determined by x-ray radiation in order to understand the possibility of borate glass as Ce3+-doped dense glass scintillator.
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