A method comprising: etching a first cavity and a plurality of second cavities into the surface of a first substrate; each of the respective first and second cavities (305, 310) comprising at least two alignment surfaces forming an alignment corner; disposing a mirror into the first cavity such that respective surfaces of the mirror and the alignment corner of the first cavity are brought into contact and urge the mirror and the first cavity into a first predetermined relationship with one another; and disposing each of a plurality of optical filters into a respective second cavity such that respective surfaces of each of the plurality of optical filters and the alignment corner of the second cavity are brought into contact and urge the optical filter and second cavity into a second predetermined relationship with one another, the method further comprising: after disposing the mirror and the plurality of optical filters onto the first substrate, disposing the first substrate into a third cavity on a second substrate, wherein the second substrate comprises one of: a plurality of optical components, each configured to receive a single-wavelength optical signal from a respective one of the plurality of optical filters, and a plurality of optical components each configured to transmit the single-wavelength optical signal to a respective one of the plurality of optical filters, wherein the third cavity comprises dimensions that substantially match dimensions of the first substrate such that the plurality of optical filters is passively aligned with the respective optical components mounted on the second substrate, wherein the first and the plurality of second cavities are arranged relative to each other so that disposing the mirror and the plurality of optical filters cause the mirror and the plurality of optical filters to be passively aligned to perform one of a demultiplexing and multiplexing function using an optical signal incident on the optical filters, wherein the plurality of optical filters and the mirror form a zigzag demultiplexer or multiplexer. etching a first cavity and a plurality of second cavities into the surface of a first substrate; each of the respective first and second cavities (305, 310) comprising at least two alignment surfaces forming an alignment corner; disposing a mirror into the first cavity such that respective surfaces of the mirror and the alignment corner of the first cavity are brought into contact and urge the mirror and the first cavity into a first predetermined relationship with one another; and disposing each of a plurality of optical filters into a respective second cavity such that respective surfaces of each of the plurality of optical filters and the alignment corner of the second cavity are brought into contact and urge the optical filter and second cavity into a second predetermined relationship with one another, the method further comprising: after disposing the mirror and the plurality of optical filters onto the first substrate, disposing the first substrate into a third cavity on a second substrate, wherein the second substrate comprises one of: a plurality of optical components, each configured to receive a single-wavelength optical signal from a respective one of the plurality of optical filters, and a plurality of optical components each configured to transmit the single-wavelength optical signal to a respective one of the plurality of optical filters, wherein the third cavity comprises dimensions that substantially match dimensions of the first substrate such that the plurality of optical filters is passively aligned with the respective optical components mounted on the second substrate, wherein the first and the plurality of second cavities are arranged relative to each other so that disposing the mirror and the plurality of optical filters cause the mirror and the plurality of optical filters to be passively aligned to perform one of a demultiplexing and multiplexing function using an optical signal incident on the optical filters, wherein the plurality of optical filters and the mirror form a zigzag demultiplexer or multiplexer. a plurality of optical components, each configured to receive a single-wavelength optical signal from a respective one of the plurality of optical filters, and a plurality of optical components each configured to transmit the single-wavelength optical signal to a respective one of the plurality of optical filters, wherein the third cavity comprises dimensions that substantially match dimensions of the first substrate such that the plurality of optical filters is passively aligned with the respective optical components mounted on the second substrate, wherein the first and the plurality of second cavities are arranged relative to each other so that disposing the mirror and the plurality of optical filters cause the mirror and the plurality of optical filters to be passively aligned to perform one of a demultiplexing and multiplexing function using an optical signal incident on the optical filters, wherein the plurality of optical filters and the mirror form a zigzag demultiplexer or multiplexer.