Ando Electric Company

Nippon Telegraph and Telephone Corporation

Masaaki Furuhashi

Ryoji Handa

Nobuo Tomita

Yoshitaka Enomoto

Mikio Maeda

Ryouji Handa

A testing method for an optical fiber is disclosed which is able to measure a loss distribution and a loss at a connection point based on a received first light signal waveform. The method comprises a step of extracting and storing the duration of the first light signal waveform when the difference of the level between the start and the end of the waveform from the specified starting point exceeds the specified criterion, a step of generating a second light signal waveform by adding the fixed values corresponding to each of the duration of the extracting result mentioned above, a step of judging if a value of connection loss calculated using the first light signal waveform exceeds the specified criterion and a step of decision of a point exceeding the criterion specified above is a discontinuous point existing in the optical fiber to be tested.

Testing method for optical fiber

The object of the present invention is to offer an optical pulse tester capable of accurately measuring waveforms of light returned from measured optical fibers even if the waveforms contain only discontinuous waveforms. An optical receiver 5 receives light returned from a measured optical fiber 10. An amplifying section 6 amplifies the level of the received light. A digital processing section 7 logarithmically converts the amplified received light level. A S/N ratio comparing means 11 compares the logarithmically converted value with a designated S/N ratio. A data storage means 12 stores received light levels having logarithmically converted values better than the designated S/N ratio, the position of the source of the returned light, and the designated gain value of the amplifying section 6. Thereafter, the procedure from the amplifying section 6 to the data storage means 12 is repeated while sequentially raising the gain of the amplifying section 12. Finally, a display section 8 corrects the level of the received light stored in the data storage means 12 based on the corresponding designated gain values which have been stored, and the data are displayed by joining them together in accordance with their corresponding positions which have been stored.

Optical pulse tester

A light pulse generator is disclosed comprising an optical loop, a pumped-light source, and an optical switch controller. The optical loop includes a light mixer, a light isolator, an erbium-doped optical fiber, a light valve means, and a light divider. The pumped-light source generates a pumped-light and introduces the pumped-light into the optical loop through the light mixer. The optical switch controller progressively turns the optical switch to an ON-state using a control signal having a gentle positive slope so that the amount of a light outputted through the optical switch is gently increased in accordance with the gentle slope of the control signal. The length of time of the positive slope of the control signal equals the time which is required for circulating a light pulse through the optical loop through one cycle. A circulation of a light pulse is carried out in the optical loop while the optical switch is in the ON-state and the light pulse having a gentle slope is picked up from the optical loop through the light divider.

Light pulse generator

An optical masking apparatus of an OTDR capable of lowering insertion loss and of easily aligning optical axes and of being structured at low cost. The apparatus comprises an optical pulse generating means, an optical branching coupler for permitting an optical pulse generated by the optical pulse generating means to be incident to an optical fiber to be measured, and an optical chopper means to which a reflected light from the optical fiber is incident by way of the optical branching coupler wherein the optical chopper means operates in synchronization with the optical pulse to remove a desired range of the reflected light. A light signal supplied to an optical/electric transducer from the optical chopper means is converted into an electric signal, which is displayed on an indicator by way of a signal processing circuit.

Optical masking apparatus

A driver circuit 2 generates a pulse current on the basis of an electrical pulse outputted from a timing generating portion 1. A light source 3 emits a light pulse according to the pulse current. The light pulse outputted from the light source 3 goes to a delay optical fiber 9 through an optical waveguide directional coupler 4, and then goes to a measuring optical fiber 10. A delay circuit 11 delays a digital operation of a digital operating portion 7, by a time required for said light pulse to go back and forth in the delay optical fiber 9.

Optical time domain reflectometer having shortened dead zone

A high power light pulse generator apparatus using an optical loop formed through a rare earth-containing optical fiber. In the optical loop, selected one of a plurality of optical fiber cords having different lengths is inserted to change the overall length of the optical loop and thus a light pulse of different pulse width is withdrawn from loop.

Growing community of inventors

Tokyo, Japan

Masaaki Furuhashi