SMC是英文Super-Multi Coating的缩写即超级镀膜的意思，是PENTAX公司的镀膜技术，据说SMC和ZEISS的T*是源于同一个专利技术的东西，当年CZ和Pentax共享这份专利。SMC发展至今已经过了好几代，每一定周期都有技术上的变化，导致各时期头的色彩特点也各不相同。

一、折射和部分反射
当光线穿过两个具有不同密度的透明物体界面时会发生折射(弯曲)，具体地说，当光线从空气中进入玻璃中，以及从玻璃中进入空气中时会发生弯曲。在理想的情况下，所有的光线都 会折射，但事实上，大约有95%的光线发生折射，而另外的5%会被反射回第一种物质中。
对摄影镜头来说，这是很严重的问题，因为最后达到胶卷表面的光线少了。对于一个折射系数为r(发生折射的光线的百分数除以100)的具有n组镜头(因此有2n个反射表面)的镜头来说，只有L比例的光线能达到胶卷表面，L = r 2n， 如果r = 0.95，n = 10,则 L = 0.36，也就是说，只有36%的光线到达胶卷。其余的光线都被散射掉了，而这其中的一些会产生令人不愉快的鬼影或者炫光。

二、Super Multi-Coating
为了减少由部分反射产生的不希望的结果，科学家们发展了化学镀膜应用到玻璃表面上，这些镀能增加r值，著名的Pentax 超级多层镀膜Super Multi-Coating (SMC),r值可达0.998!对于10组镜片的镜头，用上面的计算，得到L=0.96，只有4%的光线损失。
SMC最早在1971年获得专利并应用，那时候Pentax还仍然在做螺口器材。为了突出其镜头组件是超级多层镀膜的，Pentax把他的镜头产品线从Takumar 和Super-Takumar重命名为 Super-Multi-Coated Takumar 及后来的 SMC Takumar。
现在，在K口器材上，SMC被用于镜头，滤镜，一些机身光学元件及各种附件。绝大部分的Pentax镜头都采用了SMC技术。所有的具有SMC的镜头在他们的命名中都有“SMC”字样。少数没有SMC镀膜的镜头都是廉价品，在命名中没有“SMC”。他们也都有其它形式的镀膜，一些甚至是多层镀膜的，但不是专利的SMC。

三、SMC的好处
Pentax在他的文献06671中宣称，SMC是“非凡的七层镜片镀膜工艺，能使每片镜片表面的反射率降低至只有0.2%。其结果是在色彩还原和亮度以及在消除炫光和鬼影两方面都得到极大的改善。”
其间，所有的镜头生产商都发展了一些形式的表面镀膜，并都宣称“表现优异”，在实际使用中，绝大多数的测试都表明Pentax的SMC仍然是主流方案中最好的。

四、无鬼影镀膜
1997年，Pentax发布了FA 43/1.9 LE镜头，第一款采用了新发展的无鬼影镀膜技术的镜头，此镀膜配方是在SMC基础上的进步，如它的命名暗示的那样，它在消除鬼影方面是非常成功的。如果你相信传闻，这个新镀膜技术是为了全自动交通识别系统而发展的。它由日本警方定购的，他们在晚上由于车前灯引起的炫光而无法辨认车牌号？(license-plates)。
从1997年开始，Pentax只在一些“精选”的镜头上采用无鬼影镀膜，这可能意味着他的应用比SMC更贵。

Introduction:

Two fibre may be joined either b splicing, which is a permanent join, or by a connection which is permits repeat coupling and uncoupling. Permanent splices have applications in long distance communication links and in the construction of integrated fibre sensor systems. Connectors are used to couple fibre transmitter and receiver modules, and devices in optical communication system.

Both types of join have the following requirements:

1) The fibre end faces must optically flat and perpendicular to the fibre axis.

2) The two fibres to be joined must be perfectly aligned.

3) The joint needs to be mechanically strong and the procedure itself must be simple and easily carried out in the field.

Experiments:

Part I, Mechanical Splice – “Ultra Splice”

This technique archive insertion losses of ~0.01dB and the mechanical strength of the join is ~60% of the original fibre strength. Other splicing methods depend on precision aligned groove techniques. The fibres to be joined are inserted into the groove and held in place either by an index-matching epoxy or by purely mechanical mean. The advantage of these methods is that they are quick and simple procedures and untrained operators can routinely achieve losses of ~0.1-0.3dB.

In the experiment, we have power in 3.00mW and power out 2.85mW, then the lost in dB is:

Loss in dB = -10 x log(2.8/3.0) = 0.22dB

Part II, Fusion Splice

Thermal fusion is the highest quality splice. In this process the fibres are aligned with precision stages under microprocessor control. A plasma touch or an electric are is the passed across the junction of the fibres fusing them together. It has typical losses about 0.1dB.

Fitel Fusion Splicer

In the experiment, we had power in 3.00mW and power out 2.90mW, the loss in dB :

Loss in dB = -10 x log(2.90/3.00) = 0.15dB

Conclusion:

In this experiment we were introduced two types of splicing, the mechanical splicing and thermal fusion splicing. The data we got during the experiment is close to or in the range of the typical value. Fusion splicing produces lower loss and less back reflection than mechanical splicing, because the resulting fusion splice points are almost seamless.

Picture Reference:

http://www.tecratools.com/pages/tecalert/splicing_guide.html
http://www.alsys.ro/en/networking/networking.php