Operation of semiconductor laser Amplifier

Operation of semiconductor laser Amplifier

Hi this stuff describes about semiconductor laser Amplifiers, and I think you will get idea about its operation.

These SLA (semiconductor laser Amplifier) are based on semiconductor laser diode (SLD). This figure shows us a semiconductor laser amplifier with length l, thickness. This active region is having excited electrons and when they force to come to ground level, amplification process occurs. Here facet reflectivity is in between 30% and 35%. We can generalize the structure of a SLA by an embedded active region with two end-facets for the input and output of light signals. The end-facets with power reflection coefficients (R₁ and R₂₎ are responsible for providing optical feedback into the amplifier. These finite reflections arise because of the discontinuities of the refractive index between the semiconductor and air. When the signal passes through active region of gain G, it will boost up.

Advantages of integrated optical amplifiers

Integrated optical amplifiers have the advantage of integrating with other guided wave devices such as power dividers leading to compensation of waveguide losses.

And also optical switches associated with integrated optical amplifiers are capable of providing loss less switching and it will reduce the cross talk.

Integrated optical amplifiers are much smaller in length than fiber amplifiers


    Throughout this article I hope you may get some thing. This provides very basic explanation and future will cover more. Comments are well come. Thank you.

ADSL Packagers in Sri Lanka TELECOM

ADSL Entrée package – This package is mainly design on home internet browsing with low cost. Specially people who are satisfied only with wed browsing and used it infrequently, because in this package ISP (Internet Service Provider) provides low free usage of 1024 Mb and charge 50cent for every additional 1Mb.User can download and upload very few files (low capacity) and he is not able to do streaming, video conferencing, etc.

ADSL Home package – This package is mainly design on home internet browsing and downloads files with low cost. Especially people who are not satisfied with ADSL Entrée package they can go this solution. When consider uplink and downlink, we can see download capacity is higher than upload capacity, because home users, they really download more than upload. We can have unlimited download capacity in this package, they fore user can download more. And ISP provides this service with reasonable monthly charge.

ADSL Xcite package – This package is mainly design for small office and home users. If they have more than one computer at house or really interesting in downloading, he can buy this package download files with reasonable cost. And small business people can buy this package because ISP supplies more uplink and downlink compare to others above packagers.

ADSL Office package - This package is mainly design for middle scale business purposes that have a LAN. They want more uplink and downlink for their needs. We can see download capacity is more than upload capacity, therefore if they want to download bulky files, can purchase this package. When we consider monthly rental, it is high. Home and small business users are not able to purchase this package due to high cost. This also unlimited package therefore users can upload and download files at any time unlimitedly. We know offices need there E-mail addresses, DNS hosting, Virtual mail service, and web hosting. Therefore SLT gives those services through package.

ADSL Office 1IP package – This package is specially design for middle scale business purposes people who are having servers. In this package ISP (SLT) gives static IP for users. Other services are same as above ADSL Office package.

ADSL Xcel package - This package is really focused on large businesses that are having number of PCs. ISP provides 4Mb download capacity therefore if users  want to download bulky files, can purchase this package. This also unlimited package therefore users can upload and download files at any time unlimitedly. We know offices need there E-mail addresses, DNS hosting, Virtual mail service, and web hosting. Therefore SLT gives those services through package. They give 5 Mb for web hosting to the users.

PAP and CHAP ; Authentication Protocols That Used in ADSL

PAP and CHAP is the two main authentication protocols that used in ADSL.

Advantages and disadvantages of PAP and CHAP

•  CHAP has a more secure procedure for connecting to a system than PAP.

Because after sending the challenge message to user, the user responds with a value that calculates with the use of a one-way hash function and send sends respond packet. The RADIUS checks the response against its own calculation of the expected hash value. CHAP uses encrypted massage that includes user name and password. But PAP uses password in clear text and is a one way step process. That can be unsecured, half way communication.

Another feature of CHAP is that it doesn't only require the client to authenticate itself at startup time, but sends challenges at regular intervals to make sure the client hasn't been replaced by an intruder, for instance by just switching phone lines.

CHAP requires that the secret be available in plain text form. Irreversibly encrypted password databases commonly available cannot be used. It is not as useful for large installations, since every possible secret is maintained at both ends of the link.

•   CHAP provide access to the server in every time

It sends challenge massages frequently to the user, Because of that the user is always connected to RADIUS. Therefore we can prevent the rick of another client replacement to the server using same line.   

Throughout this article I hope you may get some thing. This provides very basic explanation and future will cover more. Comments are well come. Thank you