Hitachi Cable is pleased to announce the development of the PLC 1X4 Wavelength Splitter for Dense Wavelength Division Multiplexing (DWDM) transmission systems. We plan to begin selling this product in October of this year.

The construction of high-speed, high-volume optical transmission networks making use of cutting-edge transmission technology continues to be driven by the expansion in Internet and multimedia services. WDM transmission systems, one of those using cutting-edge technology, are able to meet increasing demands for data transmission by increasing the number of wavelength channels available. Because WDM systems represent a more economical solution than adding new fiber-optic cables, they are becoming more and more popular. DWDM transmission systems placed in 10 Gbit/s high-speed transmissions lines, another method for meeting the ever-increasing needs for information transmission, also continue to add channels.

One way of creating a DWDM transmission system that is able to handle more channels is to make the optical multi/demultiplexer itself able to handle more channels. However, because the wavelength per channel is narrow, it is very difficult to design an optical multi/demultiplexer that can properly separate signals in adjacent channels and meet the specifications for all channels.

The wavelength splitter appears to be the solution to the above problem. A wavelength splitter combines or splits wavelengths, meaning that the original spaces of wavelengths are expanded several times before wavelengths are combined or after they are split. This makes designing an optical multi/demultiplexer easier.

Hitachi Cable began manufacturing a 1X2 wavelength splitter in January of this year. Since there will be increasing demands for information transmission, the Company is aware that it needs to develop products that will contribute to the creation of DWDM transmission systems and optical multi/demultiplexers with more available wavelengths.

Hitachi Cable's 1X4 wavelength splitter combines signals with a wavelength of 100 GHz into signals with a wavelength of 25 GHz, and splits signals with a wavelength of 25 GHz into signals with a wavelength of 100 GHz (see figure 1). This allows for a DWDM transmission system that can accommodate twice the number of channels in the same spectrum as would be possible using a 1X2 wavelength splitter.

Our 1X4 wavelength splitter possesses the following advantages:

1)	Using highly accurate PLC manufacturing technology, we have achieved split wavelength error1 rates of less than 0.01 nm. This has allowed us to produce wavelength channels of 25 GHz, something impossible for other systems.
2)	Use of an optical circuit designed to compensate for wavelength dispersion makes it possible to minimize the signal's wave shape deterioration even when transmitting at 10 Gbit/s.
3)	It is possible to realize low crosstalk (less than -30 dB) by leveraging the optical circuit's highly precise accumulation technology.

Wavelength splitters not only make it easy to use multiple channels, they allow for adding channels to existing WDM transmission systems and construction of systems to which additional channels can be easily added. Because wavelength splitters allow for simple system expansion, Hitachi Cable feels that demand for these products will increase.

We estimate that sales of wavelength splitters for the next three years will be 4 billion yen.

1)	Split wavelength error: An error in a signal wavelength that has been split. When such errors are large, signal loss or crosstalk can occur.

Manufacturing Site for This Product:

Takasago Works
880, Isagosawa-cho, Hitachi City, Ibaraki Prefecture, 319-1418

Table 1: Waveguide 1X4 Wavelength Splitter Specifications

Item	Specification
Wavelength spectrum	C-band, L-band
Insertion loss	6dB or less
1.5dB bandwidth	14 GHz or greater
Adjacent channel crosstalk	-25 dB or less
Nonadjacent channel crosstalk	-30 dB or less
Wavelength scattering	Less than +/- 50 ps/nm
Size	141mmX148mmX24mm

Image 1: Using a 1X4 Wavelength Splitter
Picture: 1X4 Wavelength Splitter