This is to announce that Hitachi Cable has developed the VOA-MUX, which combines a variable optical attenuators (VOA) and a multiplexer (MUX) in a single device.

A VOA is a device that adjusts the strengths of optical signals with different wavelengths. When an optical signal is amplified using a fiber-optic amplifier, the rate of amplification differs depending on the signal's wavelength. This makes reception difficult, since each channel has a different signal strength. Solving this problem necessitated technology to eliminate the difference in signal strength, which led to the development of VOA devices. A VOA device located in the transmitting portion of a network makes for uniform optical output to the receiving portion by coordinating the optical input through adjusting for such characteristics of optical paths as the differences in amplification of each channel and transmission paths losses characteristic of certain wavelengths.

Dense Wavelength Division Multiplexing (DWDM*1) systems are rapidly being adopted, and the use of optical amplifiers in next generation DWDM systems will increase for the reasons outlined below. This means that VOAs will become necessary components of these next generation systems.

1. Optical Add/Drop Function

The spread of the Internet and last mile broadband solutions such as Fiber To The Home (FTTH) have necessitated a flexible transmission network that can handle the diverse requirements of different services as well as the dramatic increase in transmission traffic. Therefore, we feel that an optical add/drop multiplexing system must be able to add new signals as well as divide and insert various signals at relay stations inside transmission paths without stopping service. Passing through the add/drop device can mean the loss of optical signals, so amplification will also be necessary.

2. Multi-Channel Function

Long distance transmission necessitates the use of a fiber-optic amplifier several times during the course of transmission to amplify signals that would otherwise be attenuated. At the same time, DWDM systems handle an increasing number of channels to cope with increases in information volume. The more channels that are used in long-distance transmission, the more important controlling wavelength differences becomes.

Using planar lightwave circuit (PLC*2) technology, Hitachi Cable developed a VOA device necessary for next generation DWDM systems in June of last year. However, we have recently started shipping samples of our product that combines a VOA with an optical multiplexer.

Our product possesses the following advantages:

1) Small Size

Our product is a fraction of the size needed to use a VOA and MUX separately. Our product is 252 mm (length) by 129 mm (width) by 40 mm (height).

2) Low Loss Rate

Losses occur in the connection between the VOA and MUX when these two devices are used separately. However, chips in Hitachi Cable's VOA-MUX are connected by fusion splicing, dramatically reducing the losses in the optical connector (approximately 0.5dB).

3) 4 VOAs on 1 Chip

Leveraging our proprietary PLC technology, we have integrated 4 VOAs on a single chip. This makes the price of our product much lower than those that do not offer multiple VOAs per chip.

4) An Internal Regulatory Function

Our product includes the ability to communicate with an outside controller giving it the ability to regulate itself using the information transmitted from the outside controller. This means that the customer need not create a controller design.

Hitachi Cable will contribute to next generation DWDM systems given its more flexible structure that can handle higher volumes with the VOA-MUX.

The VOA-MUX is produced at
Takasago Works
880 Isagosawa-cho, Hitachi City, Ibaraki

*1

Dense Wavelength Division Multiplexing This is one type of communications technology that uses optical fibers. Technology that allows for the rapid increase of transmission volume in a single optical fiber by having a single fiber transmit many signals at many different wavelengths simultaneously is called Wavelength Division Multiplexing (WDM). Adding wavelengths is an economical way of increasing transmission volume, especially when compared with the costs of adding more transmission paths. Higher density WDM is called Dense Wavelength Division Multiplexing (DWDM).

*2

Planar Lightwave Circuit (PLC) This technology creates an optical circuit on a quartz circuit board using semiconductor processing technology such as photolithography and dry etching to create the microscopic structures of IC and LSI. Different features can be realized by using different patterns.