L. Reekie

Er(3+):Yb(3+)-codoped fiber distributed-feedback laser.

We report what is to our knowledge the first fiber distributed-feedback laser using a single Bragg grating at 1.5 microm written directly into a 2-cm-long Er(3+)-doped fiber codoped with Yb(3+). We obtained robust single-frequency operation by either using one end reflector or locally heating the center of the grating to create the necessary phase shift.

Simple multiplexing scheme for a fiber-optic grating sensor network

A new approach for the interrogation of a large number of fiber-optic grating sensors is proposed and demonstrated for a small number of sensors in which signal recovery is achieved by matching a receiving grating to its corresponding sensor. This technique is demonstrated for both quasi-static and periodic measurands, and the resolution achieved for a single sensor–receiving grating pair for quasi-static strain is 4.12 μ∊.

Tunable single-mode fiber lasers

Tunable laser action has been obtained in Nd3+- and Er3+-doped single-mode fiber lasers. In the case of the Nd3+-doped fiber, an extensive tuning range of 80 nm has been achieved. Tunable CW lasing also has been observed for the first time in an Er3+-doped fiber laser, which has an overall tuning range of 25 nm in the region of \lambda = 1.54 /mu m.

Efficient single-frequency fiber lasers with novel photosensitive Er/Yb optical fibers

Boron- and germanium-doped highly photosensitive cladding is used in a novel design to achieve photosensitive Er/Yb-doped fibers, permitting short, strong gratings (length approximately 1 cm, reflectivity >99%) to be written without hydrogenation. The high absorption at 980 nm in Er/Yb fibers permits efficient pump absorption over a short device length, which is ideal for achieving highly efficient single-frequency fiber lasers. Both single-frequency Bragg-grating reflector and distributed-feedback lasers with slope efficiencies of 25% with respect to launched pump power have been realized in such fibers.

Grating-frustrated coupler: a novel channel-dropping filter in single-mode optical fiber.

A low-insertion-loss, all-single-mode fiber, wavelength-division-multiplexing filter comprising a four-port polished coupler and a strong fiber grating is demonstrated. The device operated in a novel way by a process we call grating-frustrated directional coupling. A fiber grating, present in only one half of the coupler, frustrates the transference of power to the other half within a narrow wavelength range. The performance of a prototype device - a 1535-nm channel-dropping filter with 0.7-nm bandwidth, 70% peak transmission, and 13-dB isolation-shows great promise for wavelength-division-multiplexing and line-filtering applications.

Photoinduced absorption change in germanosilicate preforms: evidence for the color-center model of photosensitivity

A new technique has enabled us to resolve the strong UV absorption spectrum in UV-exposed germanosilicate preforms. Our results show, for the first time to our knowledge, that the large photoinduced absorption changes between 165 and 300 nm (~700 dB/mm at 195 nm has been observed) can account for, ~3 ×10(-4) of index change at 1.5 µm. The thermal-annealing dynamics of the photoinduced absorption changes also resemble those of fiber gratings, evidence that the color-center model of photosensitivity plays an important role in the photoinduced index changes in UV-written fiber gratings. We also find that the photoinduced absorption changes depend linearly on germania (i.e., germanium dioxide) concentrations in the preforms, and their exposure-time dependence can be fitted with a stretched-exponential function.

Novel add/drop filters for wavelength-division-multiplexing optical fiber systems using a Bragg grating assisted mismatched coupler

We have demonstrated a novel add/drop filter for use in wavelength-division-multiplexing (WDM) optical fiber systems based on a Bragg grating assisted mismatched coupler. The device is potentially easy to fabricate and stable, because it is not interferometric, unlike all similar devices demonstrated so far, and, therefore, does not need fine tuning of the interferometers during fabrication and does not have to maintain the balance of the interferometers during its lifetime.

Acousto-optic superlattice modulator using fiber Bragg grating

Summary form only given. Fiber Bragg gratings (FBGs) written with ultraviolet light are becoming of increasing importance in fiber systems because of their high performance, versatility, and excellent physical characteristics. In this paper, we report a technique that transforms a FBG into a Bragg cell or acousto-optic modulator operating in reflection mode.

Efficient diode-pumped single-frequency erbium:ytterbium fiber laser

We report a 7.6-mW single-frequency fiber laser operating at 1545 nm, using for the first time an Er/sup 3+/:Yb/sup 3+/ doped fiber and a fiber grating output coupler. The laser did not exhibit self-pulsation, which is a typical problem in short three-level fiber lasers, and had a relative intensity noise (RIN) level below -145.5 dB/Hz at frequencies above 10 MHz. The linewidth of the laser was limited by the relaxation oscillation sidebands in the optical spectrum and was typically less than 1 MHz.<<ETX>>

Er/sup 3+/-Yb/sup 3+/ and Er/sup 3+/ doped fiber lasers

Single-mode fiber lasers operating at approximately 1.57 mu m are described. Output powers of >2 mW are reported for laser diode pumped operation. Direct comparison is made between fiber lasers using sensitized erbium (Er/sup 3+/ and Yb/sup 3+/) and erbium on its own. The performance of Er/sup 3+/-Yb/sup 3+/ fiber lasers is analyzed in more detail as a function of fiber length. Both CW and Q-switched operations are studied and the results obtained demonstrate that practical sources at 1.5 mu m are available from diode pumped Er/sup 3+/-Yb/sup 3+/ systems. >