Jocelyn Lauzon

Development of a miniaturized integrated optical spectrometer for the infrared spectral range

A miniaturized, planar-grating optical spectrometer for the 2 to 6 micrometer range has been designed and fabricated. This has entailed development of a slab waveguide structure suitable for the infrared, a broad-band optical grating structure and fiber-based, IR input/output optics. Broad- band light is coupled into the spectrometer through a pig- tailed IR fiber and is subsequently dispersed into its spectral components and can be focused either onto a thermo- electrically (TE) cooled HgCdZnTe detector array or an IR fiber array. Integration of the optics and detector provides exceptional optical alignment and a very compact package that is suitable for various airborne and terrestrial applications.

Design, fabrication, and characterization of holey fibers

Since the beginning of optical fiber communications, many fiber designs, driven by the desire to extend the fiber limited performances, have been proposed. In the last decade, the most innovative concept that came out is probably the HF (Holey Fibre). This new fiber design consist of a pure silica fiber with a periodic array of air holes running along the length of the fiber. Usually, the air holes forming the cladding region are arranged in an hexagonal lattice and the introduction of a defect, absence of a hole, in the center of this periodic structure creates the core of the fiber. Over the past few years, impressive possibilities offered by this new type of fiber have been demonstrated in various fields of optical fiber technology such as single-mode fiber, high optical power guidance, polarization control, dispersion compensation, soliton propagation, continuum generation, fiber lasers and amplifiers, remote sensing, etc. In this paper, we review the technology and present our design, fabrication capability, as well as some results obtained with our HFs.

Influence of H2 loading on the performance of a cladding-mode-suppression photosensitive fiber

Cladding mode coupling loss below 0.1 dB for a 30 dB fiber Bragg grating are reported for a wide range of H2 treatment pressure up to 1500 psi. Extension of the photosensitive region into the clading was used for reducing the cladding mode coupling. It is shown that to take proper advantage of this, one must use a wider laser scan beam. Otherwise, the cladding mode coupling loss may increase as the H2 pressure treatment is raised. The benefit of a properly matched photosensitivity obtained by matching the Ge concentration in the core and cladding regions is also highlighted. The fiber was also designed to match a standard single-mode fiber in order to lower the average splicing loss below 0.03 dB and the attenuation to about 0.2 dB/km at 1550 nm.

Gain-locking method for dual-stage optical amplifiers

WDM systems require some means to lock the gain of surviving channels when one or several channels are added or ndropped. The pump loss method is particularly interesting but, to our knowledge, has not been applied to multiplestage namplifiers. This paper reports on a modified pump loss technique for the gain locking of dual-stage amplifiers.

Optical fiber amplifiers: a comparative study of oxide- and non-oxide-doped glass fibers

The prospect of using optical fiber amplifiers made of rare- earth doped glasses other than the very familiar silica glass opens new applications and new amplifications windows. A literature survey has been conducted in order to assess the current situation in regards to these alternative technologies. Clearly, despite the amount of efforts, the 1.3 micrometers spectral region is still looking for a more efficient candidate. So far, Pr3+-doped ZBLAN is the technology of choice, offering quantum efficiencies of about 1.5 percent only. On the other hand, the current 1.55 micrometers fiber amplifiers offer nearly unbeatable performances. Other than rare-earth silica fiber amplifiers, only fluoride and tellurite glasses rare-earth doped fiber amplifiers applications is currently in a prospective state, although the potential of these technologies is undeniable. In these cases, the huge step between bulk glass and fiber fabrication remains to be made and/or optimized.

The RISQ network as an R and D catalyst and test bench

The RISQ (Réseau dInformations Scientifiques du Québec) research and education network has been a trail-blazer in the development of privately owned fiber networks, by implementing an optical fiber owner model. This model allows RISQ to have a gracefully upgradable network that is at the forefront of the large bandwidth optical communications technology. It also allows RISQ to offer a parallel network that can be used as a test equipment for the R&D community, in universities, research institutions or the industry; a real in-the-field fiber optic network test bench. RISQ is in a privileged situation to influence optical communications R&D work. It is aware of the real needs of the telecommunications industry. It is also aware of the technological needs of the next-generation networks. RISQ suggests that telecommunications R&D should be focused on increasing network reliability and decrease network operations and capital expanses, rather than on increasing their capacity. A key to decreasing expanses would be to avoid SONET network management on long-haul trunks, without affecting the transmission quality of service. IP over optics should thus be reinstalled as a priority in the telecom R&D world. RISQ thinks optical 3R might be the solution that will allow IP over optics. As for the next-generation networks: flexibility, reconfigurability, in order to offer lightpaths of adjustable bandwidth to the user; while wasting a minimum of the valuable network bandwidth, is where we believe efforts should be concentrated on.

Environmental and optical power testing of high attenuation fibers

Cobalt-doped high attenuation fibers were tested in terms of temperature, humidity, and optical power. The maximum attenuation variation recorded was less than 3% for temperatures between -40 to + 65°C under uncontrolled humidity. When the humidity was controlled, the maximum attenuation variation was less than 3% under the worst case: +85°C and 85% R.H. Optical power test were carried out at 1W and 1550 nm over 12 minutes without any recorded damage to the fibers.

OISL transmitter at 985 nm

For high data rate (greater than 1 Gbps) Optical Inter- Satellite Link (OISL), a compact laser transmitter with high power and good efficiency is required. A trade-off analysis between the technologies such as the mature 840 nm laser diodes, 1064 nm diode-pumped solid state laser and the more recent 1550 nm Erbium Doped Fiber Amplifier (EDFA) is used to find the optical solution. The Si-APDs are preferred for their large detector areas and good noise figures which reduce the tracking requirements and simplify optical design of the receiver. Because of significant amount of power needed to close the link distance up to 7000 km (LEO-LEO), use of 840 nm diodes is limited. In this paper, we present an alternative system based on a system concept denoted as the SLYB (Semiconductor Laser Ytterbium Booster). The SLYB uses a polarization maintaining double-clad ytterbium fiber as a power amplifier. The device houses two semiconductor diodes that are designed to meet telecom reliability: a broad-area 917 nm pump diode and a directly modulated FP laser for signal generation. The output signal is in a linearly polarized state with an extinction ratio of 20 dB. The complete module (15 X 12 X 4.3 cm3) weighs less than 0.9 kg and delivers up to 27 dBm average output power at 985 nm. Designed primarily for direct detection using Si APDs, the transmitter offers a modulation data rate of at least 1.5 Gb/s with a modulation extinction ratio better than 13 dB. Total power consumption is expected to be lower than 8 W by using an uncooled pump laser. Preliminary radiation testing of the fiber indicates output power penalty of 1.5 dB at the end of 10 years in operation. We are presently investigating the fabrication of an improved radiation-hardened Yb-fiber for the final prototype to reduce this penalty. For higher data rate the design can be extended to a Wavelength Division Multiplexing (WDM) scheme adding multiple channels.